linuxaudio.org

Hallo,

Brad Fuller hat gesagt: // Brad Fuller wrote:
> That's right. According to the MIDI Detailed Spec (version 4.2) on page

quoted text
> 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__