Hacker News Reader

Comment by NikolaNovak | Hacker News Reader

That was my first thought too, but,vast vast majority of synthesizers only understand equal temperament. At best you can adjust starting point I.e. What frequency is A4. How would you even send the appropriate frequencies via midi?

This isn't a fancy keyboard layout over the standard equal temperament notes / frequencies. If I understand it correctly, this is a generator of just intonation frequencies. This will not sound "in tune" of played next to a regular synth I think.

View on HN

From what I know, typically people would use a pre-bend to achieve microtonalism in MIDI. In MIDI, like in most strictly-musical encodings, notes are specified in terms of semitones, with cents modifying those values. A cent is defined as 1% of a semitone. With a tuning reference (f), like 432 Hz, we can calculate the frequency a number of steps away with this handy function:

  f' = f * 2 ^ (i / 12)

where f' = frequency to be solved, f = reference frequency i = steps/interval (semitone distance from reference)

This works with micro-semitones, and/or negative values. So for example, if we want to know what 1.5 steps above 432 Hz is we would plug in the variables:

  f' = 432 Hz * 2 ^ (1.5 / 12) ~= 471.0993 Hz

In the case where you know frequencies, and want to get the semitone steps, you're taking the base 2 log. So,

  i = log2(f' / f) * 12

Now you'll have the note value of the exact frequency, and you can use the decimal part to set your pre-bend.

With the two directions' functions defined it's not so hard to go between frequencies and "notes". And no, you won't be in tune with most gear unless you're using 12TET A5=440Hz

That is a most thorough answer and I appreciate it very much :-)

It's possible to generate 12 ET too, by rounding all the keys and harmony changes. Just as 12 ET is a good approximation to Just Intonation, Just Intonation is also a good approximation to 12 ET. The tones lose some accuracy but gain compatibility with MIDI interfaces.

However, it would be hard for me to implement this feature, since I have no midi devices, no midi experience, and my browser (Firefox) also doesn't support WebMIDI.

I'm thinking about implementing record-and-replay, since the playback and storage-format are already done, but midi will likely be deprioritized unless there is significant interest.

Reply on news.ycombinator.com