PianoDisc 228 CFX Attack Time Delay
For Peabody Computer Music's PianoDisc
Craig Stuart Sapp <email@example.com>
20 November 2002
The following picture is a three-dimensional plot of the timing delay
for every possible MIDI note and attack velocity. The left-right axis
is the MIDI attack velocity, going from 1 (soft) on the left to 127
(loud) on the right. The MIDI notes are arranged on the near-far axis
with the lowest notes being in the lower left side of the picture and
the highest notes being in the upper left side of the picture. The
timing delays are displayed on the vertical axis. The delay is the
time it takes between sending out a MIDI message from a computer and
the time that the same note returns back to the computer from the
Note that louder pitches take less time to return than softer
pitches. This is because of the physical time it takes the piano
levers to be moved. Softer sounds require the levers be moved slowly,
and loud sounds require the levers to be moved quickly.
At loud attacks, the timing delay is around 50 milliseconds for
all pitches, although 45 milliseconds is about the fastest possible
round trip time for very high notes. The cause of the 50 millisecond
delay is that the software for playing the piano buffers the MIDI data
to correct for simultaneity problems between loud and soft notes
received at the same time.
This picture was created by averaging 200,000 random pitch/velocity
specified notes over the course of about 5 hours. Each pitch/velocity
point was played about 10 times. These values were averaged together
to remove any timing glitches in the measuring process.
Here is the same data as given in the 3D plot above. The pitches are
along the y-axis, and the attack velocities are along the x-axis.
Note the loss of feedback at low velocities. This picture describes
the quiest notes which can reliably be played on the piano for each
pitch. Note that the mid range is particularly stiff, and it requires
a higher attack velocity to play any notes in the midrange. This has
been adjusted by Michael by putting teflon powder on the leather hammer
knuckles. I will be doing another velocity/pitch timing analysis and
see how the pictures has changed.
Notice the sharp change is sensitivity between MIDI notes
47 and 48. This is a breaking point between registers on the piano,
but was particularly large on this piano. Note 48 was balanced at
74 grams, while note 47 balanced at 63 grams. Ideally regulated
grand pianos should be 54 grams at the low end and smoothly transition
to about 47 grams in the high registers.
It is interesting to note the probably change between white and
black notes in the picture. There are jagged delay responses which
alternate high/low for every other key, in general.
Here is the raw timing data used to generate the picture below:
The following plot is only a style variation of the previous picture:
The next sequence of plots displays the amount of time it takes for a
round trip to the computer for different octaves of the note "C". If
the timing value is zero in the plot, this means that no notes were
ever returned to the computer for that attack velocity. This implies
that notes played with attack velocities around those values will be
unreliably played. You should avoid those regions if you want pitches
to always sound when playing notes from the computer. This data will
change since the piano has been regulated in the midrange.
Here is a view of the time dela versus attack velocity. This pictures shows the worst possible delay for all notes. The x-axis is the attack velocity from 0 to 127, and the y-axis is the amount of delay in milliseconds
Minimum Reliable Velocity Values for each note on the Kawai PianoDisc in room 311C.