When Karl Ellison asked about a MIDI file editor in MMD 060411,
he immediately got my attention.  The reasons Karl gave have been
a concern of mine for a long time:

> I need to adjust MIDI files I'd like to play on the site that were
> either recorded at an unpleasant tempo, or the volume fluctuations
> on a reproducing roll MIDI file are bombastically exaggerated.

As I continue to learn to use MIDI in my own work, I have been made
aware that there is a general state of confusion about MIDI.  The
confusion I speak of deals with the intended use of a MIDI file.

The two broad categories of use within mechanical music users are

1. Storage and playback of data taken from paper rolls, or like medium;
2. Emulation of an instrument using stored data.

Unfortunately, there is seldom a distinction of these two very
different applications.

In my case, I don't care about any emulations.  I use MIDI to replace
a paper roll and nothing else.  Thus, the MIDI feeds my mechanical
machine with exactly the same data as the paper would do.

Unfortunately, it is now common to "listen" to MIDI files that one
acquires for free on the Internet.  If the source is a reproducing
piano roll, the "performing" computer produces synthesized sounds
of a piano.  Herein lies the problem that Karl wants to fix.

While the "on" and "off" events of the piano notes are played back
with synthesized voices with great accuracy, the dynamics of those
notes _may_ have little to do with the expression coding that was
on the original piano roll.

These dynamics are products of someone's computer program that has
been written to emulate the piano expression system.  I have no idea
of how many of these emulation programs exist, but it appears there
are several.  Some of them are just horrible as the author does not
understand the roll coding he/she is emulating.

More than likely, the files that have offended Karl's ear, do not
contain any data of the original roll coding.  To "fix" the file is an
impossible task.  For Karl to use a MIDI editor to make the files sound
better on the AMICA web site, he would need to access the original MIDI
data and implement a good emulation program that can reliably interpret
the expression coding of the roll.  Changing the tempo is an easy task.
The MIDI editor will have several options.

It is very regrettable that so many reproducing rolls are in circulation
in MIDI format with poor emulation.  In some cases, it would be better
if there were no emulation of dynamics.  Some MIDI editors could be
used to "set all velocities" to a given value, thus making the file
sound like an 88 note roll.

The best way for Karl to fix the problem is to post MP3 flies of real,
properly regulated instruments playing real rolls.

Bob Taylor
http://members.socket.net/~rtaylor/aeolian_pipe_organ.html