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I need to loop a lot of recordings such that the loop is not clearly hearable. For example, I recorded some sounds in the forest and want to loop them such that I can fall to sleep when listening them. If the sounds simply start from the beginning the "loop point" is clearly hearable and annoying.

My first thought was to cut a clip in half, then start with the second half and let it end with the first half. Then I have some freedom in cross-fade the start and end strategically such that no obvious loop is hearable.

In practice though I believe this would not always work smoothly. For example lets say you have a track where you walk through the woods. When cross-fade over a period of 5 seconds, it would be hard to match/overlay the footsteps and other contents such that it doesn't sound like you're stumbling or running for a brief moment. If the cross-fade is too short, it would become more hearable (e.g. suddenly faster wind, or faster walking, other environment). But when longer, there are basically two recordings hearable at the same time for that moment.

Since this seems to be tricky, I wonder if there is software dedicated to deal with this problem?

For both Mac and Windows (to make this question more useful).

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6 Answers

Hi softdrink, i dont know if it can help but i made a small application for my self (and a masseur friend ) using max/msp for the same reason you described. you can load .wav or .aiff choose the fading length, press play and the app plays all the sounds you loaded,fade them automatically (you can also record it - and has an an extra beat freq generator if you like) it is only for osx though. i dont know how i can get in touch with you from here though, i m new to the site, but i'll be happy to share it.

Here is the link.

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Sounds interesting. Perhaps you can upload it and give us the link if you want to share it with the public. –  Softdrink Aug 6 '12 at 16:07
    
as i said before it is a small utility i made for my self so no instructions however there are hints on mouseover written for a friend. it is a simple player not editor or such, I hope it does what you were looking for. dl.dropbox.com/u/96750291/Om_Waves.pkg –  Fumei Aug 8 '12 at 13:02
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There's no magic tool that I know of.

The technique you describe is the way to do it, it's just a question of choosing the right length of crossfade. With rythmic sounds though, it can be difficult to find the right point. I generally find that ambient sounds (like atmos) work better with longer fades and sharp rythmic sounds (like engine cycles) work better with short fades. This avoids the doubling problem you describe.

It's not ideal in some situations though, such as the one you suggest. If the footsteps are out of sync by a lot then you might be able to get through with some improvised editing. Are there any suitable wild tracks of the environment you can use as filler? Edits are often easier if you can use another sound to mask your crossfade - a gust of wind or some rustles on a third track might work well. And if the steps are out by a small amount then maybe you can gently time-stretch them into place.

If the steps are in sync and you want a slow crossfade for atmos, but are getting a doubling on the footsteps then you could attenuate some of the footsteps on the track you're fading in with a spectral editor. I've had some really good results using the lasso tool in the spectral editing mode of Adobe Audition. You can literally draw round sounds spectrally and reduce their amplitude. I think you can do this in Izotope RX2 too.

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These are some great tips. I use Soundtrack Pro or Logic for editing, and at least STP does have a spectral view. Also got Adobe Soundbooth, the predecessor of Audition. Do you know if this one also offers the spectral view and lasso tool? –  Softdrink Aug 6 '12 at 14:08
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Furnei that sounds like it could be useful for the community : )

As far as looping goes, what I generally do is -double the audio region after itself -equal power crossfade between the 2 -consolidate them in to one (to render the fade) -cut them back at into 2 at their equal parts -copy the first section of the second region to the begining of the first -render the entire first region -LOOPS

That sounds so much more complicated typed than it is in practise. But has always worked for ambiences for me : )

Thanks C

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In iTunes you can open Preferences, then check and adjust the "Crossfade Songs" option. If you put your clip on repeat it will crossfade. As I was trying this out sometimes it would work and sometimes it wouldn't, so fiddle with the time fader if its not doing what it's supposed to. If you want precise control then you may want to look into a free digital audio workstation. I haven't used any but I've heard FL Studio (http://www.image-line.com/documents/flstudio.html) is pretty good. Something like Loop Editor (http://www.audiofile-engineering.com/loopeditor/) looks up your alley too but it'll cost you.

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oops, FL Studio costs too… there is a free DAW called Podium (zynewave.com) that popped up on a google search. –  Evan Jerred Aug 6 '12 at 0:06
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One trick I have used is to have a short segment of the ambient recording laid back-to-back with itself, but reverse the second clip. When I tried it, it didn't sound repetitive at all - it really depends on the context though. In my case, it was a recording of crickets!

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I'm sure there are a couple of apps for this - one that is only recently no longer available is Redmatica KeyMap Pro, which is intended for editing/mapping sounds for Kontakt/EXS24 etc but it has a bunch of different algorithms for seamless looping... They got bought out by Apple recently & their site is gone, but via wayback machine: "Loop the unloopable with Escher, Penrose, Moebius DSP Machines and AutoLoop"

http://web.archive.org/web/20101110093439/http://www.redmatica.com/Redmatica/Keymap_Pro.html

And this is the other one - Infinity is an app thats been around for years: http://www.antarestech.com/products/infinity.shtml

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Infinity is not being upgraded to OS X? That's an curious business decision. I wonder why not. –  Steve Urban Aug 9 '12 at 17:02
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