Non Beat-Synced Time Stretching in Software

Greetings. I’m not sure if this is a technique or an equipment post. The technique I’m trying to pull off is a variation of the old tape technique of slowing down tapes relative to one another, except I’d like to avoid a change in pitch. I specifically want to do this on my computer or iPad.

I’m looking for a time stretching function like you get in Qu-Bit Nebulae (the phase vocoding side) or the Octatrack, where it’s possible to slow down or speed up a sample without altering pitch, and without reference to a project’s tempo. And with decent definition – the Nebulae v2 offers this, the Octatrack gets gnarly fast. (This can be good but isn’t what I’m looking for here).

I have lots of granular software but in all my attempts the granulation is really obvious. I am looking for something more subtle; I imagine phase vocoding will get me there. What I have tried about don’t like: iDensity; Live (seems to require BPM reference); Bitwig sampler; Quanta; Spacecraft; Granulator II; and a few others.

Maybe one of these already does this and I’m just not enough of a wizard to figure it out?

The only way I can think of doing it right now is recording in loops from Nebulae v2 into Live one by one but that’s more laborious than I want (ie, less fun) and doesn’t allow for realtime modulation.


Maybe in Reaper with the right algorithm and stretch markers ?

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since you like the sound of the Nebulae, i would say try using the mincer opcode in Csound. I find it shines at variable speed+constant pitch transformations.


I wonder how straightforwardly you could tweak the Nebulae default instrument so that the “pitch” knob changes the relative speed difference between left and right loops (rather than overall pitch). Would that create the effect you’re after?

(Caveat: I skimmed the default instrument code years ago, but I’m nowhere near familiar enough with Csound to know how gnarly this “simple” suggestion could be)

Ok this is what I was thinking about, but maybe I did not understand what you are trying to achieve :

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Thanks. Yes, that might just do it if the files don’t have to have tempo information.

Alas, I don’t program and don’t have the desire to learn at the moment, so tweaking code is not an option for me.

Might be worth checking out Emission Control 2 if you haven’t already:


I don’t remember what paulxstretch sounds like in shorter values, it might be optimized for really long things but maybe it’s worth a shot?


Metasyth? M pretty sure you’ll be able to do it in there

It’s really for longer samples. Sounds great though, and I love that it’s on iOS now.


You mentioned already phase vocoder.
If you want to use academic software, check Super VP from ircam.

If you want it super simple, we make this at work. It combines spectral synth and granular engine. Just drag and drop a sample into the plug-in and adjust playback speed or scan through the sound with the position control:

The VP algorithm was created in house with emphasis on quality.

Paul stretch was already mentioned, it is really good. The lib has got an update as well with improvements to transient preservation. Also, it is free and should be in anybody’s arsenal.

There are also different approaches. Some wavetable synths for example allow creation of spectra from samples. You can then use wavetable position to scan and do speed manipulation. The effect can sound pretty robotic sometimes.


Found this Akai S-series sampler style software that might be of interest?: The AKAIZER Project

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I second Reaper, it’s super flexible to do time stretching and can be used in full for an unlimited trial (but well worth the small fee if you decide to use it more). Check out some tutorials on youtube, it’s quite easy without having to learn too much.


Indeed… The way the stretch markers can be placed and then you can adjust start and end speed, it is so flexible and sounds really ok if not abused… I use it a lot for sound design. Add volume and pitch envelope and you have a designer’s dream !


this time-change capability is built right in Pro Tools track headers, the algorithm is fairly transparent but also there’s an unquantized varispeed option that I love for drums.

this is why I truly love using PT for non-gridded electronic music, you don’t need to define the tempo to change the timing. you can simply stretch by eye to put things where you want them. I also use it very frequently in post when I need to adjust the timing of a music cue.


The fact that this is in ProTools and Reaper made me think I wasn’t digging deep enough in Logic and Live, which I already own.

Logic didn’t yield anything (they have a “Tempophon” mode now which is hilarious but not helpful for my purposes). But it can be kludged up in Live. If you set a clip’s time stretching to “Complex” or “Complex Pro” and mess with its BPM you can achieve some nice subtle stretching. I had to figure out that I need to lengthen the clip appropriately because the markers don’t automatically move. This can also be done in real time as part of a performance but it’s not recorded as automation so it needs to output to another track. But that beats spending more money or learning another DAW.

It sounds easier to do in ProTools and Reaper but for all the respect I have for Reaper, I can’t imagine learning another DAW unless I absolutely have to.

I still would love a plugin that would just take a file, not worry about diving a BPM and allow me to accelerate or decelerate in real time and automate it, but I guess we’re not there yet, odds.

Thanks again everyone. I’ll be using this for my final Jamuary piece on the 31st.


Did you try some of the other options in Logic besides “tempophon”? I think some of them can be pretty transparent if you pick the right mode, and can be completely tempo independent.

yep, reaper works great for this…but, having added live into the mix recently you can do it there too. I don’t do time synced music much and do this type of stuff often. if you grab the item while holding shift key you can stretch as much as you like. you can then change the algorithm in the box. I find tonal sounds tend to sound more realistic in the complex or complex pro settings. you can consoladate and keep time stretching, eventually it will sound like shit tho.

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I did but they all seemed to want me to set markers and stuff. The manual was…not helpful and I honestly get very impatient with YouTube tutorials.

I agree, search results for these things are terrible- there is a lot more complex functionality available for using flex markers and such, but the basic thing you want to do, as I understand it, is just:
-hover over the edge of an audio clip
-hold option (icon should change to indicate stretch mode)

From here you can mess with the stretch algorithms.