RE: Defining pitch bend resolution

There is no authorative definition of pitch bend resolution. It's
basically whatever manufacturers have decided to implement. 95% of MIDI
instruments implement 8 bit pitch bend controllers and more recent ones
may be 10 bit. The only full 14 bit controller is the Moog MIDI
Theremin.

How reception is implemented would likewise be manufacturer and
instrument specific. Conceivably members of the same instrument family
(like all Sound Canvas products) could vary in implementation, though
this is unlikely since operating code and hardware is usually recycled
from generation to generation. Even though the Sound Canvas does not
quantize pitch bend reception to 8 bits it is possible that other
instruments do.

What you have uncovered is the underlying pitch resolution or pitch
quantization of the instrument, whether adjusted by pitch bend or any
other controller, envelope, LFO, etc. Manufacturers (except Symbolic
Sound and Justonic) never publish these specs, and very few people have
investigated them. Generally the pitch resolution is in the 0.50 to
1.56 cent range for wavetable/sampler type instruments and is limited by
hardware. It would be interesting to see if the newer DSP based
physical modeling synthesizers have better pitch resolution, though most
of these do not support tuning tables.

The change in timbre you hear is probably due to the sample
interpolation scheme used by the Sound Canvas hardware.

John Loffink
john.loffink@compaq.com

>
> Does anyone know of an authoritative definition of pitch bend
>resolution? I used to think it was obvious. I used to think that if
>a sound module had a pitch bend resolution of, say, 8 bits, that meant
>that whenever it received a 14-bit pitch bend signal it used only the
>leading 8 bits and ignored the remaining 6. But then I did some
>experimentation and discovered that this is far from the case.
>--------------------------- (snip)
> The absolute error in pitch introduced by resolution coarseness
>stays constant. For the Sound Canvas the pitch always changes in
>minimal increments of 1.56 cents. This can be calculated e.g. from
>the first line of the above table (200 cents divided by 2 to 7th
>power), but the same result is obtained if it is calculated from any
>other line. Hence, regardless of the range setting, 1.56 cents is
>always the maximum tuning error the Sound Canvas introduces into a
>played interval due to problems of resolution. The average error over
>many played intervals could be expected to be about half that.
>
> --Bill Cooper
> U. of Calif., Berkeley
>
>


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