AuTranspose

AuTranspose is a simple pitch-shifting / transpose utility plugin with a range of +/- one octave in semitones, and a +/- 100 cents detune (semitone up or down).

Please note that AuTranspose has audio latency (see the PLEASE READ section below) so it is not really suitable for realtime pitch shifting in situations where timing is critical - for example, shifting the pitch of an instrument as you play it or syncing multiple tracks in a live performance.

AuTranspose is an AUv3 effects plugin that can run standalone, or in any AUv3 compatible host such as Logic Pro, GarageBand or AUM. AuTranspose currently runs on iPadOS / iOS (iPad & iPhone) and macOS (Intel & Silicon) and is available as a Universal Purchase from the Apple App Store.

If you’re planning on using AuTranspose on Mac / desktop, please ensure that your favourite DAW / host supports AUv3 (not just AU).

PLEASE READ THIS SECTION CAREFULLY!

AuTranspose uses a pitch shifting technique that adds latency (delay) to the processed audio. Please note that this is unrelated to your audio interface buffer size or sample rate. The quality of the pitch conversion is a compromise between low latency or decent quality results - unfortunately, you can’t have both. AuTranspose can get as low as around 25ms latency which is just about good enough for a guitar octaver type application, but will probably sound a bit “wobbly” / “lo-fi” on more general audio. If you’re interested in a more guitar-centric octaver, please check out OttavaBassa which uses similar DSP, but tuned for guitar.

AuTranspose does not report its latency to the host! This is by design. Instead, the current latency is shown on the UI in samples (and ms) so you can decide yourself if you need to compensate for it - for example, when remixing projects and you need to re-sync tracks that aren’t going through AuTranspose.

So what is it for, and why did I make it?

In my own search for a simple pitch shifter, I found that the really simple ones didn’t sound so good, and the ones that did produce good results were fairly complicated and / or CPU intensive. So I tried to make something that was very simple to use, that produced reasonable results.

When might AuTranspose be useful?

Backing tracks: You might want to transpose up or down by a semitone or two to put the song in a more comfortable key to sing, or perhaps you tune your guitar to Eb. In these situations, you could probably transpose the whole track up or down and it’ll still sound OK. The only other thing to keep in mind is that the playback of the track will be delayed by the latency so as long as the backing track doesn’t have to sync with anything else, you should be fine.

Remixing recorded projects: Perhaps you have a project that’s audio only and you’ve decided it needs to be in a different key. You could use AuTranspose to pitch-shift the tracks or stems that need to be in key, but leave the percussion tracks as they are. You can then add a sample length delay (*) to th