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MMD > Archives > September 2001 > 2001.09.20 > 05Prev  Next

Transcribing Piano Rolls to MIDI
By John A. Tuttle

[ Ken Loesch wrote to John Tuttle: ]

Hello John,  Your name pops up all over the place when player pianos
are keyed in search engines!

I am interested in building a piano roll to MIDI converter.   I'm an
electrical engineer and I'm familiar with optical sensors which would
be suitable for this.  A couple of things that will present a challenge,
though, I thought you might be able to help me with:

1. What would be the easiest way to build a roll transport which
incorporates the tracking mechanism?  I can't seem to find much about
exactly how this is done on a real player piano.  I would like to use
a small low rpm dc motor to move the rollers.  I don't need variable
speed, since MIDI programs can adjust tempo.  I would however need the
roll to remain in alignment with my 88 (or so) optical sensors.

2. For the QRS rolls which you sell, is the hole spacing 9 per inch
on center?

3. I can't find a specification to show exactly where middle C should
be punched relative to the left edge of the roll.  I would need this
to correctly position the optical sensors.  Do you know what this
measurement is?

Any info you have would be greatly appreciated.

Ken Loesch <>

 - - -

Hi Ken,  There are people with tons more experience in roll-to-MIDI
conversion than me, and many have written about their trials and
tribulations in the Mechanical Music Digest (491 articles containing
the word MIDI in the Subject) .  You can access the Archives at:

Yes, the spacing is 9 holes/inch on center.

I've never measured the distance from one edge to middle 'C', but the
QRS Test Roll plays middle 'C' first.  You can purchase it directly
from QRS for $10.75.  Their telephone number is 1-800-247-6657.  By
my ruler, it measures exactly 6-1/8" on center from the left-hand edge.
The paper is 11-1/4" wide.  (Now I've measured it...  ;-)

Tracking systems normally work in conjunction with the units
transmission.  Since you won't have a transmission, you will have to
use a system that moves the trackerbar, or install simple guides.
Optimally, you will be able to adjust the lateral position of both the
spool chuck and the takeup spool so that no tracking device is

One system I can think of that utilizes a 'moving trackerbar' is the
Ampico Reproducing system, and it employs 'finger sensors' that touch
the edges of the roll.  However, like all tracking systems, it only
reacts 'after the fact', and using such a device would require a vacuum
source (approx. 15" of water vacuum).

Furthermore, such a system would not do a good job tracking rolls with
damaged or curled edges, which are quite common on old rolls.  Point
being that a manually adjustable system would seem to me preferable
to all other possibilities.

Hope I've been helpful.


John A. Tuttle

(Message sent Fri 21 Sep 2001, 00:12:39 GMT, from time zone GMT-0400.)

Key Words in Subject:  MIDI, Piano, Rolls, Transcribing

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