Hello Co-readers !  In his letter from 3 September Wayne Stahnke leads
our attention to a certain part of the coding technique from the editors
of Ampico A rolls to give single notes in a chord different accents.

Presuming the chord is recorded exactly as the artist played it, the key
of the note to be accented is pressed a bit sooner than the other ones.
The finger for this key was held a bit more stiff, striking its key first
and a bit more hard.  ( I only hope Robbie can agree ;-).

 [ Agreed!  Rachmaninoff strove to play this way; the roll-editor also
 [ helped the artist to sound as he *wished* he could play!  -- Robbie

How to code the dynamics for this?  It's easy to see.  The intensity was
set higher before,  and then -- immediately before the chord -- canceled.
The intensity shows a low-going ramp from this moment on until the lowest
point is reached or a new coding begins.  Each following note will sound
lower than the previous one.

In many cases there is only one note accented by striking sooner and the
other ones together a bit later at once.

Since each answer raises a couple of new questions:  How are the holes in
the trackerbar shaped? (I made "pencil prints" of a couple of different
ones.)  How long are the different tubes?  How fast travels the pressure
signal in them?  (Mach 1?)  How fast will the vacuum fall after the
cancel hole appears?  How are the curves of vacuum shaped?  (I suppose
not linear).

Following Yousuf A. Wilson the raise of vacuum from 5" to 25" takes about
0.18 seconds, but to fall from 25" to 5" takes 0.9 seconds minimum.  At a
roll speed of Tempo 90 the paper moves about 45 mm in a second, e.g.,
it takes 0.022 seconds to travel one millimeter.  That is more or less
how much the accented note is preceding its sisters on the roll.

If many interested people work together good exploration can be done.
One good task would be measuring and comparing dynamic curves of suction
on many pianos of the same kind.  Unfortunately I lost the name of the
journal where Yousuf A. Wilson wrote about this subject.  Who knows it?

Best regards, Horst Mohr
mohr@nemeter.dinoco.DE   H. Mohr Koelnerstr.49 51515 Kuerten 02268/1561

 [ I have asked Wayne Stahkne if he could also provide a Duo-Art roll
 [ for the tutorial using "View", since Ampico rolls and pianos are
 [ pretty rare in Europe and the UK.  What is your opinion of the
 [ "View" program, Horst?  -- Robbie