The Pitch Bend Saga

Friends,

For those of you who have been following the pitch bend tuning
saga, I received the following today from Tom White, the president of MMA,
which confirms Gary Morison's previous suspicion:

From: Tom White
To: "'Andrew Souter'"
Subject: RE: Pitch Bend Specifics
Date: Sat, 16 Nov 1996 13:13:08 -0800
MIME-Version: 1.0

>For the last couple of weeks I have been trying to find out how
>exactly the MIDI Pitch bend signal as specified by MIDI standards
>effects the output frequency of a given synthesizer.

The MIDI specification (for whatever reason) does not specify
how a synthesizer should respond to pitch bend messages.
This lack of definition is true for many areas of the specification,
and as MIDI has become more popular as a "distribution medium"
this has become a popular topic for discussion.

The General MIDI specification was developed in response to
these issues, and thus defines (more so than MIDI itself) some
of the responses a synthesizer must make to MIDI messages
(in a General MIDI system). However, even General MIDI may
not go far enough for some people.

Addressing just the pitch bend question, GM does define the
_extreme_ ends of the pitch bend messages (2 semi-tones), but
allows this to be changed using a well defined pitch bend
sensitivity message. However nowhere is there any
definition of the "response curve" .. which is apparently what
you are seeking. I suspect the reason for this is that the nature
and typical use of pitch bend gives little reason for that exactness.
However, I have no doubt that you have a unique example which
would invalidate my claim .

Anyway, the most likely answer to your questions is that
every manufacturer (and possibly individual products from the
same manufacturer) pitch bends differently, but it is also likely
that they either do a linear bend or some other "common" curve.
Unfortunately, the only way you will ever know is to ask about
every product ....

Not much help? Oh well ... good luck on your search!

- Tom White
- President, MMA

-andrew

Safe Journey...



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