Changing audio speed "cleanly?"

Doug_Marshall wrote on 11/20/2015, 10:47 PM
I have a very personal reason for making this request: Does anyone know an audio tool that can change the speed (but not pitch) of a music track (pipe organ, in this case) without garbling the audio with artifacts? An elderly friend of mine did a very nice performance during a video session a while ago but he gradually slowed down a little as it went along. As a result, he doesn't want me to post this particular video - and he is no longer well enough (leukemia) to re-record it. I feel that as much of his playing as possible should be out there for people to hear because his style is unusual and interesting. With the right tool, if it exists, I know I could fix it to his satisfaction. Any suggestions?



Jamon wrote on 11/21/2015, 12:56 AM
Right-click the audio clip in Vegas Pro
Time-stretch / pitch shift method: élastique
Stretch Attributes: Pro
Ctrl+resize the clip

Try the other methods to see which works best.

Or click "Audio Track FX" for the audio track, and see if it has the "élastique Timestretch" plugin. Also try the "Time Stretch" plugin.
Grazie wrote on 11/21/2015, 1:29 AM
@Jamon, it was this that made me dismiss Elastique: "but he gradually slowed down a little as it went along."

Jamon wrote on 11/21/2015, 2:29 AM
Select audio track
Insert, Audio Assignable FX...
Select "élastique Timestretch", Add, OK
Insert, Audio Envelopes, FX Automation...
Select "élastique Timestretch", Enable "Time stretch ratio", OK

Double-click on the line, or right-click Add Point where the playing speed changes
Twice at the start point, twice at the end point
Drag the inner line down to make it go faster when he plays slower
Right-click the line parts and use the Fade options to make more natural curves
JohnnyRoy wrote on 11/21/2015, 7:50 AM
Here is the technique that I use. I call it "Tempo Mapping":

Open the audio in the trimmer. Listen to the playback and drop a marker at the start of each measure. Save the markers in the file. (these will be media markers)

Drop this file onto the timeline. Determine the tempo of the audio by listening to the first few measures. Drop timeline markers at even intervals for each measure. This will mark your fixed tempo.

Finally, split the audio at the internal media markers and Ctrl+Drag the edge to drag it to the next timeline marker. This will sync each measure to the original tempo.

It's tedious but a very effective way to map a live performance to a fixed tempo and you won't perceive any change because each measure makes a small correction that should be undetectable.

Silverglove wrote on 11/21/2015, 10:09 AM
The time compression/expansion algorithm in Vegas 12 and 13 is atrocious. Anything that I ever have to do using this method, I go back to any version prior to these. If you are not hearing the abnormalities, you should go back and do a side by side comparison.
CJB wrote on 11/21/2015, 10:30 AM
Ableton Live is probably the best choice. You can probably get a demo/limited free version to do what you want. Anytime you muck with the tempo there is risk of artifacts. (just like applying noise reduction).
riredale wrote on 11/21/2015, 11:44 AM
Elastique is wonderful. Or at least as it exists on V9c. I've used it many times both to nudge pitch change (if an a cappella choir slowly goes flat) and also for speed adjustments. It is a far better tool than the standard stretching tool that was part of Vegas prior to V9. Far better in terms of transparency as regards clicks and other artifacts. Have no idea how Elastique sounds of recent versions of Vegas, however.

As an aside, one of my most satisfying projects ever was about five years ago. Two recordings of the Durufle Requiem, the first one with a very good ensemble, and the second a month later with a very good pipe organ accompaniment (and no other instruments). Both with the same 40-member choir. With Elastique I was able to use one as a reference and then slice up and stretch/compress the other to sync with the first. Hundreds of cuts and lots of labor involved, but the results were remarkable--an 80-voice choir with expert accompaniment including pipe organ.

So what you want to do is a piece of cake. Just slice it up and gradually speed up the pieces as you go along. There will be a limit as to how much increase can be gained without artifacts. You'll need to find out.
Doug_Marshall wrote on 11/21/2015, 12:23 PM

Fascinating to hear about your project with the Durufle. Sounds like a great idea - and challenge! I suspect your tempo adjustments would have been quite small, although the detail and time involved would be the exact opposite...

I need to bump the tempo about 15 points (on elestaque's scale) by the end of the piece I'm trying to edit and the artifacts get quite nasty and extraterrestrial-ish. In *some* ways, YouTube's speed adjuster at 1.25, though way too fast, is less obnoxious. In your project, I'm guessing that one performance could provide smoothing and cover for the other, for a very listenable result. Fun!

In any event, if elastique is it, I guess I'm done! Sigh...

Let me know if there's anything else out there anybody can recommend.

Jamon wrote on 11/21/2015, 6:53 PM
There's a Vegas Pro Audio forum:

There are many possibilities. But if you don't want to only use Vegas Pro, you might need to spend money and/or learn something new.

You can start by taking a glance at time-stretch related software:[]=643&tg[]=7837&tg[]=68

It might be better if you upload the raw file, and ask an audio forum to try to fix it. Then you'll have access to a wider range of technology and experience.

But I wonder why it needs to be fixed at all. That sounds more like a psychological issue than technological. Musical performances are often more about the people than the technical sound. The story around the performance makes the imperfections powerful. Personally, if someone were to link it to me, I'd be far more interested in watching the authentic version. To me, by modifying the performance it'd be ruining it. Like taking a natural beauty, and giving her cosmetic surgery.
Doug_Marshall wrote on 11/21/2015, 9:19 PM
Hi Jamon,

Thanks for those links. I'll definitely be paying them a visit!

The issue about the tempo is tough philosophically and, in an ideal world, we'd just re-record. But the location is 1,000 miles away and the gentleman who was playing is elderly and now quite ill, so it's probably more practical to work on the tempo in the studio. Other than artifacts, the tools in Vegas bring it around quite well, musically speaking.

Dancerchris suggested Ableton Live and I'm beginning to have a look at that. Like most products these days, it does so many things that it's either a holiday feast or your worst nightmare, depending on your point of view, but we'll give it a go!

riredale wrote on 11/21/2015, 11:57 PM
By the way, if you're talking about a 20% increase in speed at the end, why not slow down the beginning by - 10% and then part way through increase to +10% ( in small increments of course)?
Doug_Marshall wrote on 11/22/2015, 2:07 AM
Interesting idea. I'll experiment with it a bit.
Silverglove wrote on 11/22/2015, 11:21 AM
This is really one of my areas of expertise. Let me know if you'd like some help with it.
Doug_Marshall wrote on 11/22/2015, 2:44 PM
Thanks! Really appreciate it. We'll see how it goes...