Audacity Forum

Hi,

I'm new to Audacity so I'm probably missing something. I tried using Effect->Change Pitch I noticed it said "Change Pitch without changing tempo". The pitch change seemed to work ok but the duration of the selection got changed too. If that doesn't change the tempo then I guess I don't understand what the tool is supposed to do. The change in length seems to be a constant. If I select the whole track and shift it up 4 semitones the track shortens by about 50 msec (not much but...). The same happens if I select a word (750 msec) and shift it up 4 semitones the length changes about 22 ms. really messes up the length and synch between tracks! I suspect this is a bug since it doesn't really show if shifting a whole track.

So the question is how do I change the pitch without changing the length?

Dave

DaBraunBird wrote:really messes up the length and synch between tracks! I suspect this is a bug since it doesn't really show if shifting a whole track.

Not really a "bug" - more of a "limitation". "Change Pitch" will change the pitch while keeping the length approximately the same. A similar limitation exists with "Change Tempo".

If the length is critical (and it sounds like it is for what you are doing)...

If you want to change the pitch of part of a track, cut and paste the sound that you want to process onto a new track before you apply the effect, then the timing of the rest of the track will be unaffected.

If the change in length is messing up the timing within a single processed section (for example a rhythm track) then split the track into sections (for example, split immediately before the first beat of each bar) and cut/paste a section to a new track then apply the effect to that section. Cut/paste it back to the original track and proceed to the next section.

Steve - Thanks for the tips - Your suggestion would work for a rhythm track where silences abound to absorb the little missing bits but instrumentals and vocals (or anything legato) really suffer. Would you know if this is a limitation of the algorithm being used or of the implementation?

stevethefiddle wrote:

DaBraunBird wrote:really messes up the length and synch between tracks! I suspect this is a bug since it doesn't really show if shifting a whole track.

Not really a "bug" - more of a "limitation". "Change Pitch" will change the pitch while keeping the length approximately the same. A similar limitation exists with "Change Tempo".

If the length is critical (and it sounds like it is for what you are doing)...

If you want to change the pitch of part of a track, cut and paste the sound that you want to process onto a new track before you apply the effect, then the timing of the rest of the track will be unaffected.

If the change in length is messing up the timing within a single processed section (for example a rhythm track) then split the track into sections (for example, split immediately before the first beat of each bar) and cut/paste a section to a new track then apply the effect to that section. Cut/paste it back to the original track and proceed to the next section.

DaBraunBird wrote:but instrumentals and vocals (or anything legato) really suffer.

For these, it's a little more complex - When you select and copy the bits for processing, you need to copy slightly longer lengths so that each section overlaps by a little with the next section. You can then apply a short cross-fade from one section to the next. It's a bit fiddly/time consuming, but it is possible to achieve near perfect results this way (ignoring the reduction in sound quality that inevitably occurs with sound stretching).

DaBraunBird wrote:Would you know if this is a limitation of the algorithm being used or of the implementation?

Without looking at, and understanding the code, I wouldn't know. The underlying algorithm is pretty effective and produces fairly good results, but I suspect that to achieve greater accuracy in the length would require a greater degree of sophistication.

I seem to remember seeing a plug-in for a "better pitch shift", somewhere. Perhaps searching Google may dig it up.