Beat matching without the wobbles

July 14, 2010 11:00 AM

How do you change tempos, yet keep the same pitch, with minimal loss of quality?

I recently recorded a track at 111bpm that I want to speed up to around 114 bpm. I used GarageBand to track live instruments using various mic setups and was able to achieve a really nice guitar tone.

The problem is when I try to speed up the recording, the guitar tone turns wobbly and distorted.

What are your tried and true ways of beat matching while maintaining pitch with minimal distortion? I'm not averse to trying different software so any suggestions are welcome.
posted by dobie (8 comments total)

dobie, just to get a little more precise, is this a guitar track that was recorded at 111 bpm that you trying to convert to 114 by using a tempo function?

In my very limited experience, I've only had good results using tempo and bpm functions for sequencing purely digital stuff. I've tried to use them for recorded instruments with the same results that you have. I don't think the software is designed to do that.

I would record the differently timed sections separately and splice them together either in the same tracks or in new ones altogether.

Disclaimer: I'm a novice and hopefully someone with more experience and knowledge will chime in and help figure this out.
posted by snsranch at 5:53 PM on July 14, 2010


This is for a few different tracks, all live instruments. I guess now that you mention it though, I could try beat matching them individually to see if the lower complexity doesn't result in distortion. But I am pretty sure that DJs do this sort of thing with regular tracks.
posted by dobie at 7:31 PM on July 14, 2010


You should try Ableton Live and Logic to see if they work better than Garageband. Also, if there is a way to do smaller chunks, one at a time, you might get better results, even though it's a pain in the ass.

Another approach would be to use Recycle to chop your track into small samples and make it squishable without losing resolution, but that would have several steps to it (I'm not sure it would be worth it).
posted by umbĂș at 8:07 PM on July 14, 2010


Ableton Live should work, and I can definitely say Propellerhead Record works for a song sped up from 128 to 135BPM.
posted by chimaera at 9:10 PM on July 14, 2010


I just tried the demo of Ableton 8 Suite and I could hear distortion. I'll give the others a chance.
posted by dobie at 9:20 PM on July 14, 2010


I've recently heard some impressive results on DI'd electric and bass guitars time-compressed up from 115 to 125 BPM using the MPEX-4 algorithm included in Cubase 5. It was definitely usable for production to my ears.

It was mostly staccato material however, not sure if that makes a difference. I have no experience with the algorithm beyond this. But I will say that it was the most transparently time-compressed digital audio I had ever heard.
posted by goodnewsfortheinsane at 7:57 PM on July 23, 2010


I've done this for remixes where i've taken the Multi-track recordings one by one in Soundforge and Time Compressed to speed it up.

If you do each part individually and tailor the algorthim to the particular part (ie the one that works best on X) then I find when you then mix them all back together it can sound ok. not too wobbly.

bass freq. often just get too wobbly though.
posted by mary8nne at 8:38 AM on August 2, 2010


It was easier to just re-record the guitar. Thanks everyone for your advice though.

I noticed that some BPMs had less distortion than others. I wonder if there is a mathematical reason for this in the algorithm. My calculus is a little out of date, but it seems like it would be related to harmonic resonant frequencies, though pitch corrected.
posted by dobie at 9:39 PM on August 7, 2010


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