Best way to time stretch?


Tore Nylund

Guest got a question about the best way to time stretch audiotracks:
Here's the problem.... while recording we've found that one old demo song would be great to include on the album... it's very well recorded with GREAT vocals so we would just have to add real drums and som more guitars.
BUT I really would like to increase the tempo just a little bit... a few more BPM would be great.
So do you think it's possible to time stretch the tracks so that we can keep the good stuff... ?
If so... there are many different ways to do a proper timestretch with many ways to do the calculations (is that the proper word? )
Wich is the best way to go?
Should we use the same algoritm(hope that you know what I mean) on vocals and guitars?
We're using ProTools TDM, Logic platinum ( Mac)and Cubase SX ( PC)... any ideas wich one that would make the best time stretch?
Is therem a limit in % of BPM where it will sound "bad"?
I would really be happy for som input on this subject.

Alécio Costa - Brazil

Well-Known Member
Mar 19, 2002
Hi Tore.
I have wirtten a very similar thread a few weeks ago. Are you a TDM user?
The advice would be more related with ourplug-insroom... Anyway, we are here to help.
Here it goes:
a)Which plugs do you have available?
b) Is your old track originally tracked with a click ?
b) What is your original bpm? What is the final one you aim?

Verify the phase after the procedure.
I would suggest Wave´s PAZ to check for weird phase problems and of course, your own gifted ears while listening to mono.

I would strongly recommend you Pitch ín time by Serato. If they have a 15 day demo free of beeps and mutes, go check for yourself .

Man, I did a mastering a few weeks ago where an album was tracked in 2 different places and bpm´s.

In the first recording session, one year go, it was done live with 45 musicians and the conductor stayed around 96 BPM.

The second, most recent recording session, most of the songs were at 116bpm, now entirely recorded with a click, where 35 musicians were divided in a group of 2 takes.

I had to speed up that old demon . First I tried with Digirack´s TC EXP.

Man, it did lots of damage to the phase, once lots of mics were used to capture the performance and probably random speed bumps/breaks were messing the calculations.

I have done a few biiiig recording sessions with lots of musicians and mics, everything was under control.

Then, I tried Pitch in time 2.01. It was 99% better and no phase-$*^t problems at all.

The tone was oka, no problems when checked in mono, etc etc.

I guess the new Waves Transform Bundle shall also do it fine and as far as I have posted at our plug-in room, Serato has just released version 2.2.

Hope it helped ya
Nice weekend


Well-Known Member
Feb 23, 2001
Silicon Valley
I would argue that if you value great sounding audio that it is never proper to do time stretching or time squeezing at all - ever. Well, with one exception and that is radio ads where you need exact length and the need for pure audio quality is not as ctitical. My experience with this type of major manipulation audio processing is that there will always be undesireable artifacts. How much this degrades the audio and how much your willing to accept are questions you'll need to consider. Without even hearing it I can already say, it would best to leave it alone as it is.

lorenzo gerace

Well-Known Member
Jan 27, 2002
Well, without getting into time-stretching ethics (to do it or not to do it?...) I'd go with Serato Pitch 'n Time: it's the best algorithm I've found so far for time and pitch manipulations; if you don't go at the very extremes of the processing range the results are stunning: I speeded up a few piano and double bass recordings (as the producer requested, I'm always a bit hesitant to do that on acoustic instruments), and neither the players coud tell I did it.

Depending on the sources you have available, my procedure would be something like this: provided that you have the correct bpm you want to speed at I'd process the prerecorded material (I guess it's a stereo file, and you don't have the tracks available to work on separately), and then once you're sure you have it speeded up as much as you want and sounding good (no phase artifacts or glitches) I'd record the new parts to it, mixing them afterwards, so the amount of time-stretched material would be just the minimum necessary, and the new parts would sound good being brand new.
If you have all of the separate tracks to work on it's usually better the opposite, mix them and speed them up, since by speeding up separate tracks you could accidentally have some time or phase glitches in between them, it's better not to risk.

This is a method frequentely used by remixers, so that they can speed up what they need (usually just the vocal, and a few lead parts) and then add the new parts at the new speed; it's better because some instruments (particualrly drums) tend to sound glitchy- cymbals and hi-hats- if speeded up too much.

Hope this helps


Alécio Costa - Brazil

Well-Known Member
Mar 19, 2002
yes, guys. For jingle production, where sometimes you end up with a sketch at 31/32 seconds, puting on a time window of 30 might be ok.
I A/B tested the 2 different SD2 stereo files , while checking in mono several times, looking at PAz and things were nice.


Also, Further to ACB's suggestion. Try Digital Performers in built algorythm

I had to use this for some aerobics tracks a few years ago, and it was AMAZING.

But the Serato products are waay cool.

Tore Nylund

Thank input..
Alécio wrote:
a)Which plugs do you have available?
b) Is your old track originally tracked with a click ?
b) What is your original bpm? What is the final one you aim?
a/ I don't know what plugs that are available in the studio ( ProTools TDM)... but I know they have most of the waves stuff and much more.... same goes with Logic... at home on my PC-DAW I thought about the time stretch function in Cubase SX.. if it's good enough.

b/ the original tracks are recorded with programmed drums so the tempo fixed. We also have all the separate tracks available...

c/ I want to increase the tempo from 105 to 110 bpm ( less than 5%)

I will check out Pitch ín time by Serato. Thank you for the tip.

AudioGaff... well sometimes I think that you can live with bad sounding stuff like undesireable artifacts if you have a killer performance and the song REALLY need that higher tempo. We just have to try if it's good enough for a rock song... and we will have most of the instruments "un-stretched"... drums, bass and more guitars will be recorded afterwards.

And again thank you a lot for your input.
I'll be back to tell you how it went.