Re: [linux-audio-user] midi note numbers

Hallo,
Brad Fuller hat gesagt: // Brad Fuller wrote:

> That's right. According to the MIDI Detailed Spec (version 4.2) on page
> 10, MIDI note 60 is Middle C.
> This is the fourth C on the piano, and traditionally known as C4 (261Hz)
> on the piano. However, I've seen apps refer to middle C as C3, C4, and C5.
> Crazy.

Well, being a saxophone player (in the past) it doesn't sound *that*
crazy to me. Why? The sax (usually) is a transposing instrument. Tenor
or soprano sax are tuned in Bb, alt saxophones are tuned in Eb. If you
put your fingers in the "C"-position, the actual frequency coming out
would correspond to a Bb or Eb on the piano, depending on sax model.

And of course with tenor and soprano sax the same finger settings
also result in a completely different octave.

Now what should midi do about it? Remember, there are not only midi
keyboards, there also are midi wind instruments, midi guitars etc. and
there are keyboards with various numbers of keys.

It sounds sensible from a keyboard point of view to just put 60, which
is about the middle of 0-127 as the middle C key. Where this middle C
key is, of course depends on the keyboard model.

For a software synthesizer you don't have a real middle key, you only
have frequencies. It makes sense to spread out the available 127 pitch
numbers so that they span most of the pitches that are musically
useful. The lowest "C" that is useful seems to be the one at about
8Hz. The C below that would be at about 4Hz which is not perceived as
a pitch anymore. You get to use the ~8Hz as lowest C if you define
pitch 69 as corresponding to 440Hz.

On the other end of the scale you get about 12500 Hz for a midi pitch
of 127. This is about half of the nyquist frequency at 44.1kHz
samplerate so there still would be a bit of headroom. However there
won't be a lot of headroom: You will pass a 22.05kHz Nyquist at a
pitch of 137 if you interpolate the midi formula for 69=440Hz this
way: mtof(137)=22350.6

So using "69 midi pitch := 440Hz" in a software syntesizer as default
range makes a lot of sense.

Ciao

-- 
 Frank Barknecht                 _ ______footils.org_ __goto10.org__