Unit of Pitch

General discussion about tracking, help and support.
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MrsBeefy
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Unit of Pitch

Postby MrsBeefy » Thu Dec 17, 2015 12:28 am

I was wondering what 1 unit of pitch in the instrument editor is equal to, i.e. how many "pitch units" are in half note step?
And is this a linear relationship e.g. 1 "pitch unit" = X amount of frequency?
I am assuming that pitch and frequency describes the same thing in this sense, or are they different things completely?

I'm decent with trackers but don't much background in music theory.
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iYamWhatIYam
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Re: Unit of Pitch

Postby iYamWhatIYam » Thu Dec 17, 2015 12:36 am

I'm fairly certain that a pitch of +1 would be one pitch lower than 0, and vice versa. This can also be applied to using the arpeggio envelope to create pitch, which is what I did in FamiTracker to create triangle toms FamiTone 2 can compile correctly.
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MrsBeefy
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Re: Unit of Pitch

Postby MrsBeefy » Thu Dec 17, 2015 12:40 am

Yeah I know how to use pitch in FamiTracker(and that up is down) and have used it a bunch, just wondering more about the technical aspects (how pitch converts to frequency).
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iYamWhatIYam
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Re: Unit of Pitch

Postby iYamWhatIYam » Thu Dec 17, 2015 12:52 am

That, I cannot answer. Perhaps HertzDevil or w7n can help you here.
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Xyz
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Re: Unit of Pitch

Postby Xyz » Thu Dec 17, 2015 1:13 am

The NES soundchip doesn't make sound based on semitones or cents or anything of that sort. It does so by division.
When you use the pitch effects in FT, you are changing the "period". On the NES the period can be between 0 to 2048. The outputted frequency is "1789773hz / (16(period+1))"

So a higher period means a lower note. A lower period means a higher pitched note. It also means that changing the period by 1 in low notes makes almost no difference while changing the period by 1 in high notes makes a very noticeable difference.

Source: http://wiki.nesdev.com/w/index.php/APU_Pulse
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MrsBeefy
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Re: Unit of Pitch

Postby MrsBeefy » Thu Dec 17, 2015 1:33 am

Thank you that's exactly what I wanted! +1 for the formula & +1 for the source too.

Another question, would you happen to know what the period value is for, say C-3?

Edit: Nevermind, I can just look up frequencies and plug them into the formula!
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w7n
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Re: Unit of Pitch

Postby w7n » Thu Dec 17, 2015 2:18 am

another thing to note is that some exp chips behave differently. note that there might be a constant added to the pitch value in the equations, e.g. freq=c1/(pitch+c2), so the words proportional or inversely proportional aren't always accurate here.
2a03, vrc6, mmc5, sn5b's frequencies are inversely proportional to the pitch value
vrc7 is proportional, but is also affected by an 'octave' value
fds is proportional
n163 is proportional to the pitch value, and inversely proportional to the waveform length and the number of channels used.
this means:
the lower notes of fds and n163 are more sensitive to pitch bends
the higher notes of 2a03, vrc6, mmc5, sn5b are more sensitive to pitch bends
pitch bending of vrc7 is not so easy to describe.

regardless of the chip, p81 always raises the frequency from p80, and p7f always lowers the frequency(although the sensitive thing is still the same)
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MrsBeefy
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Re: Unit of Pitch

Postby MrsBeefy » Thu Dec 17, 2015 2:52 am

Thanks for the extra info!

But who uses expansion chips anyway... ;)
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MiniMacro
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Re: Unit of Pitch

Postby MiniMacro » Thu Dec 17, 2015 3:40 am

a lot of people
wow this is total BS
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Xyz
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Re: Unit of Pitch

Postby Xyz » Thu Dec 17, 2015 11:04 am

MrsBeefy wrote:Thank you that's exactly what I wanted! +1 for the formula & +1 for the source too.

Another question, would you happen to know what the period value is for, say C-3?

Edit: Nevermind, I can just look up frequencies and plug them into the formula!

FT doesn't always use exact A440 tuning
http://famitracker.com/wiki/index.php?t ... y_register

FYI, the thing you are asking for is called FT's "period table" and many sound drivers for all kinds of different chips have one of these.
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