Time stretching (and time expanding !) is an useful feature for those who produces remixes, mashup / bootleg, or want special FX.
Time stretching consists in changing the speed of a sound without changing its pitch.
The inverse operation is called pitch shifting : changing the pitch without modifying the speed.
Wavosaur has no native timestretch feature but Wavosaur has two pitch modifiers :
- Simple pitch shift
- High precision FFT pitch shift
The simple pitch shift modify the speed when you change the pitch : it acts like a goold old turntable if you set your 33 rpm LP record to 45 rpm => pitch increase ! welcome to the chipmunks.
The High precision FFT pitch shift is a special effect for changing the pitch without changing the speed.
These two features are in the “Process menu”
and now the magic :
Let’s try with a vocal sample, open it in Wavosaur :
this is the normal vocal sample without any treatments
now go to menu -> Process -> Pitch Shift -> High precision FFT, and let’s change the pitch to an extreme setting : X 2 (one octave higher)
this is the pitched chipmunkized version of the vocal sample!
and now, go back to the original pitch : menu -> Process -> Pitch Shift -> Simple : and now set the pitch one octave lower ( – 12 semitones) : this will also change the speed (two times slower)
this is the time expanded version
with these two operations you obtain a time stretch / expand : pitch is the same, but speed as changed ! This is more effective for voices, solo tracks… but don’t hesitate to experiments.
Just don’t forget your calculator, if you need to make something less trivial than one octave up / down.
The FFT pitch shift can be long to compute, you can also use free pitch shift VST plugins instead of the native Wavosaur effect.
Here’s some freeware plugins for pitch shifting (without changing speed):
download here : http://www.ochremusic.com/specMonkyageSt.zip
download : http://bitterspring.net/pitchshifter/