Sliding Stretch - Does it Overwrite or is it Additive?

I am running Audacity 2.3.0 under Win 7/Pro X64.

I began playing with Sliding Stretch last night. I applied it to a sine tone and found with experimentation that I could transform the selected portion of a track into a sine tone where the frequency slowly increased. How to select the Initial Pitch Shift and the Final Pitch Shift so that it could be applied to a 40 sec of a 60 sec mono 880 Hz track and end up with one that started at 800 Hz and ended at 1000 Hz was not an intuitive process.

In playing with the effect, I began to get the impression that its impacts are additive. Is this true?


It replaces the original audio with the processed version.

Thank you, Steve,

Just to be certain I understand you correctly, do you agree that running Sliding Stretch two or more times on the same waveform in the same track results in replacement audio each time, so that the end result is ‘additive in terms of the ultimate starting and ending frequencies?’

As I learned by doing last night, if the wave form is relatively simple, Analyze>Plot Spectrum run on selections at the start, middle, and end will tell the user the range and amplitude of the fundamental peak frequency, as it will for any point on the track of interest to the user.


Yes. If you apply a pitch shift of +1 semitone, and then apply (to the result of the first pitch shift), a pitch shift of +1 semitone, the result is approximately the same as if you had applied a shift of +2 semitones to the original.

However, note that applying a sliding change multiple times produces a slightly different sweep than applying a larger change once. This is a similar effect to what happens if you apply a “Fade” effect multiple times; the fade “shape” becomes noticeably curved.