Developing Dirk's Piano Tuner turned out to be a job with a
lot of small struggles and large battles.
The targets were set to an almost impossibly high level.
- The tuner had to automatically recognize every note
accurately, within a very short period of time.
- It also had to perform at least as fast (preferably a lot
faster) than the classical system of "tuning by ear".
Personally I lacked the knowledge in the area of
piano-tuning. Fortunately I have a friend, passionate piano amateur Ben Verbon,
who lives in the Dordogne in France.
He had all the knowledge that I didn't have. That knowledge
and his perfectionism and his never-ending forbearance, have proven to be
essential in the development of this tuner.
We have worked together on this project for two long years.
I wish to state my gratitude for the never-ceasing support
he gave me, in his challenges and his instructions.
Table of contents
tuning of a piano
number of important terms
and placement of the microphone.
tuning process with Dirk's Piano Tuner
accuracy of the tuner
Tuning a piano the classical way is a very complicated
process. One has to possess the skills, to handle the tuning hammer in the
correct manner and to leave the tuning pin in a stable position. It takes time
and practice to master these skills. It is however even more difficult to
determine the correct pitch of the strings. Many instruments can be tuned using
a simple tuning device. Each tone is then tuned exactly to a predefined
frequency. This method can't be used tuning a piano. The result would make the
piano sound harsh and out of tune. The reason for this lies in the way stringed
instruments produce their sound.
A string can vibrate in several ways. It can vibrate in one
whole section ; the middle of the string then oscillates and the ends are
fixed. It can vibrate in two sections; the middle and the ends are then fixed
and the string oscillates on 1/4 and on 3/4 of the length. This way a string
can also vibrate in three, four, five... etc. sections. All these vibrations
occur at the same time in the string.
Each vibration has its own frequency. A struck string
therefore provides several frequencies at the same time. These are called the
strings' harmonics. When these harmonics are exactly 2, 3, 4 and 5 times the
base frequency, then a simple tuning device can be used. For a piano this is
unfortunately not the case. For a piano these factors are not exactly 2, 3, 4,
and 5. The exact values of these factors determine the base frequencies of the
piano strings, that is when the piano sounds most harmonic or "in
tune". In practice it shows that the low tones need to be tuned a bit
lower. The high tones need to be tuned a bit higher. The rate in which the low
tones need to be tuned lower and the high tones higher is called the stretch of
the piano. This means that each piano has to be tuned differently to achieve
its optimal sound and performance.
There are already tuning devices that take this stretch into
account. You can choose a stretch at setup, where a small stretch is chosen for
a large piano and a large stretch for a small piano. Such tunings devices can
take the piano to an almost optimal tuning. But the specific design of the
concerning instrument is not taken into account and therefore some of the
factors, that decide the stretch, are left out. Because of this, the piano will
not sound optimal and it will still be necessary to determine the optimal
stretch "by ear".
The piano technician does this by striking a lot of
intervals (two keys at the same time) and aligning them. To do this properly, a
lot of experience is an absolute necessity. The difficulty lies in the fact
that you cannot tune the intervals entirely pure and the rate of purity is
different for each and every interval. When an interval is not entirely
correct, one of both notes will be adjusted accordingly. This note however is
also part of several other intervals. Therefore all these intervals will have
to change as well. All this produces a large complex puzzle that has to be
Dirk's Piano Tuner solves this puzzle for you.
In Dirk's Piano Tuner all strings will be recorded by
playing them all one by one, only one string per tone, the remaining strings
muted. The tuning (and so is the stretch) is determined by the computer using
these single string recordings. The tuner not only records the fundamentals,
but also the harmonics. After this "single string" recording, the
tuner has all the data needed to calculate the optimum base setting of all
strings. The tuner calculates then the purity of all possible intervals and
aligns them. After this the strings can now be tuned one by one to the
resulting tones from the tuner. The tuner recognizes the struck string
automatically and shows how much the string deviates from its ideal pitch. The
muted strings are later on tuned equal to the earlier tuned string in the same
string set. After tuning all strings the piano has been tuned with the optimal
stretch. The piano now sounds as pure as possible for that particular piano.
Each string needs only to be tuned once and it is no longer necessary to finish
the tuning by ear.
The trial version is meant for getting a good idea of the
possibilities of the tuner. As with the full version, the trial version can
record all notes. After that, the optimal stretch can be calculated. The trial
version calculates the optimal frequencies of all As (A0 - A7) and all Es (E1 -
E7). These tones can then be tuned. All the tones in between cannot be tuned.
This way it is possible to tune a series of intervals over the entire range of
Octaves: A0-A1, A1-A2 etc. E1-E2, E2-E3 etc.
Fifths: A0-E1, A1-E2 etc.
Fourths: E1-A1, E2-A2 etc.
The tuner can be extended with modules. These extension
modules add extra functionality. At this moment there are no extension modules
available yet. Check the Internet site for new extension modules: http://www.dirksprojects.nl
the number of waves per second of a tone (pitch).
the total range of wavelengths that can be perceived by the human ear.
sound with a fixed pitch.
notation indicating a tone with a specific pitch and length.
increasing or decreasing sequence of tones in a fixed order.
the perceived frequency of a tone. This is the fundamental frequency.
tone or tonic
the perceived pitch. The lowest tone of the collection of tones that make up a
a tone in a sound that has a higher frequency then the tonic. The overtones are
multiples of the tonic.
a beat(ing) occurs when two tones with a small difference in pitch sound at the
The difference in pitch between two tones.
the smallest musical interval in western music. An octave exists of twelve
semitones. In an equal temperament all semitones are evenly divided in
frequency. On a piano the interval between two adjacent white keys, is one
semitone, if there is no black key in between. If there is a black key in
between the adjacent white keys, then the interval between the two white keys
is two semitones. In that case the interval between the white keys and the
black one is one semitone. The interval between a tone and the same sharp tone
(for example C and C#) is always one semitone.
the difference between two tones where the second tone has twice the frequency
of the former.
1 Octave =
• Tuning or
the way in which the combination of frequencies for a specific range of tones
on an instrument are selected. In Western music the equal temperament is most
popular. Other temperaments are for example: the just intonation, the
Pythagorean tuning, the mean tone temperament, the well temperament and the 31
a chromatic scale is a scale that contains all twelve semitones within an
c – c# – d – d# – e – f – f# – g – g#
– a – a# – b (the white and black keys of a piano)
and whole-tone steps
a half tone step is equal to an interval of one semitone such as the interval
between two adjacent white keys on a piano without a black key in between. A
complete tone step is equal to an interval of two semitones such as the
interval between two adjacent white keys on a piano that do have a black key in
a diatonic scale is a scale with half and whole-tone steps:
C major: c – d – e – f – g – a – b (the white keys on a piano or the buttons on
a diatonic accordion)
C minor: c – d – eb – f – g – ab – bb
unit for frequency.
1 Hz = 1 wave per second.
logarithmic unit for the difference in pitch with respect to a tone in the
1200 Cent = 1 Octave.
100 Cent = the distance between 2 successive semitones in an equal temperament.
all frequencies that occur in a sound. The frequency spectrum can be presented
in the form of a graph.
The accuracy of the microphone
For the tuner only the frequency of the measured sound is
important. The sound volume does not matter. The sensitivity of the microphone
is not important. The accuracy of the measured frequency is. This is however easily
sufficient in any microphone.
Externally connected or built in
A built in microphone such as those present in the most
laptops, is not always usable. It catches more surrounding noise than an
externally to the sound card connected microphone. The case of the laptop
catches up sounds and vibrations and passes them on to the microphone. The
cooling fan of the laptop is an important source of surrounding noise. A built
in microphone can also often not measure the lowest frequencies. Another, much
larger, disadvantage of the built in microphone is that it is impossible (or
difficult) to position it right with respect to the instrument. An external
microphone, which is connected with a wire to the sound card, can simply be
placed on the desired location.
The distance from the microphone to the piano
The closer the microphone is placed to the piano, the
smaller the influence of the background noise in relation to the sound to
record. So a shorter distance will improve the measurement.
Some microphones are supplied with software (so-called
drivers) which can modify the sound signal by using digital effects. These are
effects such as 'echoes', 'hum filters', 'stereo enhancement', 'direction
sensitivity' and 'noise suppression'. These effects can distort the recorded
sound as a result of which the tuner will not function properly. Therefore
effects have to be disabled. On the other hand, microphone settings such as
'boost', 'sensitivity', 'volume', 'gain' and 'balance' are of no consequence.
An external microphone with a cable connected to the
computer is the preferred configuration, because it can be easily placed in a
proper location. That means that a simple microphone connected to your
computer's soundcard will suffice. The frequency range of such a really cheap
microphone is in most cases not known. A high quality dynamic microphone will
give better results, especially in the lower frequencies. Generally spoken a
USB microphone will do too. In that case, the internal sound card of the
computer is not used, which can be an advantage. The much more expensive
condenser microphones are usable, but they won't give you a better
tuning-result. At all times, digital effects in the microphone software have to
Hovering the mouse-cursor above a button or a window, will
show a "tool tip". A tool tip is a small text box with explanation about
that particular button or window.
Select the sound input
To be able to use the tuner it is necessary to select and configure
the desired sound input channel. Generally this will be a microphone. When you
start up the tuner for the first time the configuration screen is shown
The left part of the configuration screen above is important
for selecting and configuring the sound input. At 'select the recording device'
you select the sound card. The different sound inputs of the selected sound
card are enumerated at 'select the sound input in the recording device'. Here
you select the sound input to use.
The resulting signal from the selected input is shown in the
graph at bottom right. The tuner works best when the input signal is as strong
as possible, but it should stay clear of the top and the bottom of the graph to
avoid distortion. The strength of the signal can be controlled by moving the
'Sensitivity' slider. When a microphone is selected and its signal is too weak,
the check mark 'Microphone boost' can be set to amplify the signal more.
If you have a stereo input with a "Balance
Slider", you'll have to set its slider in the middle.
The button 'Windows Recording Control for the selected
device' opens the sound input configuration screen of Windows. This screen is
normally not necessary.
Sometimes a hum (50 or 60 Hz) is audible on the input. This
is generally caused by either bad earthing or a bad power supply. It can be
taken out by checking one of the hum filter boxes.
Not using these filters can result in unwanted detection of
certain tones e.g. G1 (49Hz), A#1 (58,27Hz) or B1 (61,74Hz).
8a. Some information
The automatic key detection
Dirk's Piano Tuner automatically detects the key that you
hit. The detected key will be marked green on the screen-keyboard. Right after
hitting or releasing a key you might see another key turn green shortly. This
is normal behavior and you can ignore that.
Striking the keys when tuning
In the piano, while hitting a key, you'll be hitting a
string set, i.e. one, two or three strings, depending on the height of the tone.
For that reason, please take note of the following.
hitting a key, only one string of the set should vibrate. It is of vital
importance that the remaining strings in a set are muted completely and are not
allowed to vibrate in any way. If this muting is not done properly, it will
influence calculation of the optimal stretch, resulting in a stretch that is
is also of vital importance that you use the piano keys to strike the
string(s), because the hammer that is connected to the key is mounted in the
most ideal position to do this. If the string is hit, plucked or sounded
otherwise, the harmonics produced by the string will be quite different and
will cause a less optimal stretch.
recording (the record button depressed) the key has to be held down until the
relative screen-key turns blinking red, which tells you that the recording is
the process of tuning (the record button not depressed) a stricken key has to
be held down until the key turns green on screen, which tells you the tuner has
recognized the tone. Once this has been done you can hit the key repeatedly.
8b. The actual tuning of a
piano using Dirk's Piano Tuner
up Dirk's Piano Tuner on your computer. Then connect and set up the microphone.
(for details see chapter 6). In case of a grand piano, the microphone can be
placed, on the floor under strings, the microphone pointing upwards. In case of
an upright piano it can be placed near its pedals, the microphone pointing at
the piano. Place the microphone on e.g. a rubber pad or a cushion, so it won't
pick up vibrations from the floor.
your screen, check in the upper left corner if the right microphone input is
a quiet environment with minimal interfering ambient noise. Especially
continuous, monotonous sounds, like the sound of a fan or an aquarium pump will
spoil the tuning.
tune a piano, first record all its tones. In the main screen of the tuner, push
the 'Record' button and hit each piano key (one by one, from low to high),
leaving at least two seconds of silence in between. Each time, keep the key
down until the tone is recorded and the corresponding key in the main screen of
the tuner turns red.
recording the piano, the lower two gauges stay blank. The reason for this is
that the optimal stretch is not yet known so the tuner cannot determine the
deviation in respect to the optimal stretch yet.
during the recording process, the tuner picks up on a background sound, it is
possible that an unwanted recording is made. In that case the corresponding key
will turn red. To remove such a recording, click on the concerning key with the
right mouse button. The red color will disappear. After that and only after
that, the key can be recorded again. After all the keys have been recorded (all
keys are a steady red), click the "Stretch" button.
As soon as all tones are recorded, go to the Optimal Stretch
Screen by clicking on the 'Stretch' button in the main screen of the tuner.
Each vertical bar in the graph you see here represents a piano
key. Each recorded tone shows its deviation from the equal temperament with a
short red line. The horizontal line in the middle represents the equal
temperament. If all tones are recorded, calculate the optimal stretch by
clicking on the 'Calculate Optimal Stretch' button.
optimal stretch for the recorded piano is now being calculated. This will take
a few minutes. During this time, the computer compares millions of combinations
of harmonics. The resulting optimal stretch is shown by the short horizontal
green bars. You will see the green lines jump up or down, getting closer to the
ideal tuning. The original recorded values are still represented by the
horizontal short red bars. This way you can see the difference between the
current and the optimal stretch. The bar at the bottom of the window shows how
far you have progressed.
10. You need to record a
piano only once. After the optimal stretch has been established, you can save
it by clicking the "Save Recording" button. When, in the future, you
need to tune that particular piano again, you can recall the appropriate "optimal
stretch" again by clicking the "Load Recording" button and
selecting the relevant file.
11. The final graph
showing the "optimal stretch" for that piano, looks a little bumpy.
This is all right. It is the "purity" of the intervals that define
the final sound of the piano. The frequencies of the tonics are less important.
12. The piano can now be
tuned using the resulting "optimal stretch". Close this window (Alt-F4
or the little red cross top right). The screen with the graph will disappear
and the main screen will reappear.
13. Now you have sorted
out the "optimal stretch", you can start the actual process of tuning
your piano. You start in the middle of your keyboard, normally C4 and start
your way up to the right, into the high section, string set by string set.
After that you start from the middle to the left into the low section. Mute all
but one string(s) in the string set. Strike the corresponding key and observe
the red needle in the bottom part of the window. This needle responds directly
to the movement of the tuning hammer. When the needle reaches zero, the string
is perfectly tuned. However a string can never be tuned perfectly, which is
really not necessary either. Sometimes the needle swings a bit around the zero.
The scale behind the needle is expressed in Cents. 100 Cent at key A0
corresponds to 1.59 Hertz. 100 Cent at key C8, however, corresponds to 241.92
Hz. If the tuned string has a deviation of less than plus or minus 0.1 Hertz,
that deviation will not be audible. You can check this deviation real-time by
comparing the desired (shown left above the tone name, in the box on the right)
and the measured frequency (bottom right next to the needle).
14. Before you start
tuning using the hammer, wait until the red needle shows the actual amount of
deviation. This takes about half a second, but it'll give you the most accurate
reading. Remember that the last movement of the tuning hammer should be in the
direction of lowering the tone. This makes sure that the build up torque
tension in the tuning peg has been taken out. If you fail to do this, the
string will detune after a short while. This takes care of on string in the
15. You now have to tune
the other strings in the string set, to the one you have just tuned using
Dirk's Tuner. In case of a three string set, first de-muffle one string and
tune the other equal to the tuned string, by listening to the beats. Then tune
the third one to the other two. This is relatively easy, because you can hear
the deviation in beats very clearly. Don't forget, that even if you have Dirk's
Tuner, you still have to develop a feeling for handling the tuning hammer, to
achieve a complete and satisfying result.
16. Having done all of the
above, the piano is now tuned according to the optimal stretch. You can check
the various intervals and chords by ear.
The input signal
The sound signal the tuner uses for its measurements is
shown in waveform in the top left corner of the tuner window. The height of the
wave indicates the strength of the input sound. If the sound becomes too strong
for the wave to fit the window, it will be scaled down. The name of the sound
input that is chosen in the settings screen (Menu - Tuner Settings) is also
shown in this window. In this window you can check if the input signal is
When the tuner detects a tone, the relative key is marked
green on the screen-keyboard. The keys of the keyboard run from the A0 up to and
including the C8. The character is the name of the tone and the digit is the
The detected tone
The detected tone is shown as a character with an octave
number and if applicable a sharp sign in the tone window of the tuner (bottom
right). The frequency of the tone is shown in the top left corner above this
character. Please note that this is not the measured frequency, but the target
frequency. Also, below this frequency character, it is indicated if the tone
has been selected automatically or manually.
The frequency spectrum of the detected tone
The tuner shows the frequency spectrum of the detected tone
graphically in the frequency spectrum window. The horizontal axis represents
the frequency and vertical axis represents the strength of the frequencies. A
struck string causes a peak in the frequency spectrum and the red waveform
represents the frequency spectrum of the detected tone. The tuner detects the
peak in the red line and marks it with a blue vertical line. The vertical grey
line indicates the frequency from the scale of the detected tone.
The deviation of the string's frequency
The string's deviation from the target frequency is shown
numerically and is also represented by a moving red needle (bottom part of the
window). The absolute frequency in numbers is shown below the deviation.
The selected tuning
The tuner shows the tone's deviation from the selected (and
previously loaded) tuning. The deviation is zero when the string's frequency
matches exactly the frequency of the selected target tuning's tone. The
selected tuning is displayed in the middle text box. The tuner supports the
"equal tuning" and the "optimal stretch". The optimal
stretch is calculated by the tuner itself and is unique for the each individual
Freeze the tuner
The movement of the tuner needle, numbers and graphs can be
stopped, to enable easier reading. Just click the "Freeze" button.
Hitting the spacebar will do the same.
Enlarge the tuner to a full screen
To get full visual access to the tuner window, enlarge the
window clicking the square box, top right of the window (see below). This is
especially helpful when your screen is positioned at a distance.
The tuner settings window can be opened by clicking "Menu
- Tuner Settings". This settings screen can also be opened by clicking the
image in the middle of the tuner.
Selecting the image displayed on the main screen
The top row shows 5 different images. Here you can select
the image that is displayed in the main tuner window.
Disable the large tool tips
When using Dirk's Piano, a socalles "Tooltip" is
shown when hovering over a component of that window. e.g. : button, window,
slider, check mark, text, etc. This tooltip is a small text box containing an
explanation about the component under the cursor. These help texts give
important information about the various functions in the tuner and are
therefore very useful. For the experienced user, these tooltips can be
disabled, by checking the checkbox. "Disable large tooltips."
The maximum accuracy in Hertz and in Cent
The accuracy of the Tuner is better (less) than 0.1 Hertz
(waves longer than 10 seconds). The accuracy in Cent gradually changes over the
range of the tuner because a Cent is a relative unit. The interval between two
successive tones in Hertz increases as the pitch gets higher while the interval
in Cent is by definition (always) 100. Some values of the accuracy of the tuner
in Cent: C1: 5.2 Cent, C2: 2.6 Cent, C3: 1.4 Cent, C4: 0.6 Cent, C5: 0.4 Cent,
C6: 0.16 Cent, C7: 0.08 Cent, C8: 0.04 Cent. So in Cent, the tuner gets
therefore more accurate as the pitch gets higher.
Detectable pitch differences
The smallest by human ear detectable pitch difference is
approximately 2 Hertz. The accuracy of the tuner of 0.1 Hertz is many times
better. This high accuracy is necessary to measure the beatings between two
strings. A difference in beating of more than approximately 0.1 Hertz is
already detectable by the human ear.
The tuner uses the sound card for its measurements. To
compensate possible errors in the sound card, the tuner carries out an
automatic calibration. Manual calibration such as those often possible on
conventional tuners (with a screw for example), is not necessary. Because of
this the measurements of the tuner are always accurate enough.
The internal accuracy
The tuner shows the measured errors with 1 or 2 decimal
places (digits behind the comma). The tuner calculates with 7 decimal places
internally. Right before an error is shown, it is rounded on 1 or 2 decimal
The Tuner runs optimally on machines starting from the
Pentium II, 1 GHz. On less fast machines the tuner also works fine, but will
react more slowly. The tuner runs under Windows 2000, XP, Vista and 7 and uses
a microphone input.
Microphone close to
the soundboard of a piano. (the case does not need to be opened)
Microphone below a
Tools to mute
strings for piano and grand piano.
Muting of a three
string string-set in the middle region (piano)
Muting of a three
string string-set in the octave (7) below the highest (piano)
Muting of a three
string string-set in the highest octave (piano)
Muting of a series
of two string string-sets on a grand piano using multiple mutes
Muting of a series
of three string string-sets on a grand piano using multiple mutes
Muting of two two
string string-set using a mute (grand piano)
Muting of a three
string string-set on a grand piano using two mutes
Muting of multiple
two string string-sets using a temperament strip (grand piano)
Muting of multiple
three string string-sets using a temperament strip (grand piano)