Audio recording and tempo changes in playback

[RBlooz]

I hope the title doesn't mislead everyone, this is really a question about recording audio at a slower tempo to facilitate technique (or lack thereof!).
In order to record a guitar part that is a bit beyond my current ability I decided to record it at a much slower tempo and then play it back at the correct, faster tempo. What I ended up with is a 2 bar guitar break that plays back in a slower tempo than the rest of the sequence. I'm a bit confused by the soundbite and waveform editors but I have a feeling the answer is in there somewhere. Can someone shed a little light on this for me?
Thanks in advance.

DP 8.07
Fastlane USB
OS 10.6.8

[Henry Robinett]

Have you tried something like Amazing Slow Downer or Transcribe?


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[buzzsmith]

It sounds like you were hoping that the guitar part that you played would somehow recognize the tempo of the destination sequence.

Unfortunately, that is not the case.

As Henry mentioned, you could transfer the recorded guitar into ASD and make the time adjustments there.

Audio quality would probably be quite suspect, however, as the doubling of the speed will most likely have a lot of artifacts.

Maybe not..,

Then you save the result and import that new audio file back in to DP.

Hope that helps!

Buzzy


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[stubbsonic]

There are a couple of ways you can approach this.

If you think of your digital audio recorder as a "tape machine"-- some audio interfaces will allow you to slow the clock down to record at a slower speed. However, with this technique, both pitch and tempo slow down together. You'd need to play your piece at a lower key to match the slowed down audio's new lower key (- so when it is sped back up it raise to the correct key). It might even be that tuning your guitar down (if it isn't too far) might do something interesting (and cool) to the sound quality when it is tuned back up.

If you don't want to deal with all the pitch change stuff, you can record as you have done, but then take your slow guitar track over to Audacity and use it's free pitch & tempo plugs to get you back to the correct tempo & key.

There's a relatively inexpensive tool called IrcamLab TS which does basic pitch shifting in a standalone app. It's pretty handy. The sound quality is better than ASD. Has a demo mode so you can see if it will be useful for you.

[daniel.sneed]

+1 on Ircam TS.
Presently, not a plugin, but standalone app.
If you tweak fine, it will do fine.
IMOE, artefacts are program dependant, but Ircam TS has proved to be ok in many situations. Even with complex audio materials.

[buzzsmith]

I'll have to take a look, too.


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[RBlooz]

Thanks for all the great suggestions. I'll check out "+1 on Ircam TS" and "ASD" and report back.

I suppose I could just hire a guitar player but that would be way too easy...

[davedempsey]

I have had to speed up audio for a client's project once - on 3 tracks of beautifully recording piano. I used the time compression algorithm in protools which is reasonably good. I found an increase of 7% was the most I could get before the timbre of the grand was altered in a negative way. Even at lesser percentage increases there were noticeable changes in the quality of the resonances but those were differences as opposed to damage
That was solo piano whereas if you are dealing with guitar that will be part of a mix I would expect you could achieve a substantial increase over 7%.
The interesting point for me would be whether a part played on guitar then sped up would have the right mojo. My guess is that the more techniques used - vibrato, bends, hammers glisando etc - the less likely such a part would be convincing.