how to change the hertz in GB?

You can use the AUPitch effect on all your tracks to alter the pitch. You'll have to do some math:

E.g., if you want to play the piano with a 432 Hz tuning, you'll have to set the AUPitch (which goes in cents = 1/100 of a semitone) to minus 31 cents.

)Here's the math: one cent up is (2^(1/12))^0.01 = 1,00058 times the frequency. Divide the frequency by the same number to go one cent down. How many cents is it to go from 440 to 432 Hertz?

1,00058^x = 440/432 = 1,01851

x*log1,00058 = log1,01851

x = log1,01851/log 1,00058 = 31,63)

^ means to raise to a power, 3^2 is 3 squared, or 3*3.

log means the common base 10 logarithm function.

If you don't have a scientific calculator, google can do it for you.

but just use the -31 cents and you don't need to know the math.

I admit it's a bit hard to comprehend because frequencies don't go linear but exponentially - each octave doubles the frequency of a tone. So to go up one semitone (in an equal tuning), you have to multiply a frequency by the 12th root of 2 (or divide by this factor to go down one semitone). One cent is 1/100 of a semitone, so it's the 1200th root of 2. The calculation computes the number of cents you need to adjust from a 440 Hz to a 432 Hz tuning.

I have tried to use AUPitch to set each track (or also the Master track insted) to -31 cent.

But GarageBand (latest Version) insists to reset it to -24 cent! (after reopening the AUPitch) 😟

Any ideas why od how to change this?

Ha! Found the mistake in GB!

The input into the AUPitch plugin is not being accepted, as long as the "Music keyboard" (Musik-Tastatur in German) is opend and visible. Closing it, everything works as it should, even with -31 cent. 🙂

Good, that we talked about it! 😝

I am not sure what you mean by tuning the *mic* to various pitches, but something like Audacity can take a "real instrument" track and alter its pitch.

I assume you mean the A440 tuning standard.

Garageband has no support for this. You can use pitch bending or some other techniques for simulating this, but it is a bit of a hack.

Well, when I import a song into Audacity and there call the Apple AUPitch, this plugin works as it should and resamples to -31 cent. Just to let you know....