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Let's say the song is at 122 bpm. And i want to decrease it by 10% to approximately 110 bpm. How much do I need to increase/decrease the pitch now to get back the original pitch of the song?

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    Is there any particular reason you can't do this in a single step? Most DAWs can change tempo without altering pitch.
    – Tetsujin
    Apr 22, 2020 at 9:57
  • I'm very new to this. I don't know what a DAW is. Let's say I have a very basic app that only allows to me bump up/down the pitch and same for the tempo. So if i took the tempo to 90%. Would you have any idea how much i would need to adjust the pitch approximately?
    – Derpp
    Apr 22, 2020 at 10:28
  • DAW = Digital Audio Workstation. Even the most basic of freeware DAWs, Audacity, can do time-stretch - manual.audacityteam.org/man/change_tempo.html
    – Tetsujin
    Apr 22, 2020 at 10:36
  • Like Tetsujin wrote - any decent digital editor can change tempo and pitch independently. Apr 22, 2020 at 14:47
  • @Tetsujin so if someone named "Jack" designs a workstation, it's a .. Jackdaw! Apr 22, 2020 at 14:48

1 Answer 1

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12 * log2(newtempo / oldtempo) = pitch difference in semitones caused by the tempo change.

For example, tempo change from 122 to 110 lowers the pitch by about 1.79 semitones:

12 * log2(110/122) = -1.79253148845872...

Another example, tempo change from 122 to 244:

12 * log2(244/122) = +12.0

i.e. exactly one octave.

BPM is a unit of frequency, the same physical quantity as "pitch", just 60 times bigger numbers. 120 bpm = 2 Hz, two beats per second. 110 bpm = 1.833 Hz.

To reverse the pitch change caused by the tempo change, pitch-shift it by the same amount in the other direction.

However, any sort of musical audio editor usually has a pitch-preserving tempo change, and tempo-preserving pitch change mode.

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