How to Stretch Audio in Reaper

Reaper is a powerful, flexible and customisable audio application. You can use Reaper for music creation and production, podcasts, voice-over, sound design, audiobooks, live performance, mixing for video, mastering, and much more.
In our free Reaper course, you’ll learn the basics of Reaper with Dave Bode, and in this lesson you'll learn how to stretch audio in Reaper.



How to Stretch Audio in Reaper

I'm going to work on my bass track for this lesson, and if you’ve been following along on this course so far, this is something you’ll remember I recorded live so it's not 100% perfect. The rhythms are pretty close but there are a few sections that could be changed a little bit to be right on the beat.
I’ve solo’d the track and brought the volume up a little bit to make it easy to hear, and now I’ll show you how to stretch the audio in Reaper.

I'm splitting the item just before the last note. You can see how it looks above.

I move my mouse to the end of the item, hold Alt or Option on the Mac, and then click and drag. You can see above that it’s stretched now.

When I do that, a rate indicator pops up that wasn't there before. It's showing me a value of less than 1, which indicates that it's longer than it was before. If you move it to the left, it'll give you a value that's greater than 1, which means it's playing it back faster than its default, which is 1.
Let's say that I make it about twice as long, which is 0.5. It would basically sound the same, it's just really, really long. There's vibrato but the vibrato is 50% as fast as it was before because it's twice as long as it was before.
Pitch Shift

I want to jump into the project settings because I want to show you that you can change the default pitch shift mode in Reaper.
Currently it's set to élastique 3.3.3 Pro. That is the default. If you click the drop down you can see that there are a number of other options, but I don't think I've ever changed it from the default setting because the default setting works for just about everything. If I do need to change the pitch stretching algorithm that Reaper’s using, I can do it on a clip-by-clip basis by hitting F2 to bring up the Item Properties.

With this media item selected, in the Media Item Properties, there's a drop down where there are all of those same options, but now I can adjust them for individual items if I want. If, for whatever reason, I felt that this pitch stretching algorithm wasn't working, I can change it to something different or I can select the same as the project default but just change the mode. This is useful if you're doing something like a vocal, or spoken word and you're stretching and it doesn't quite sound right.

What you can do in that case is experiment with one of the different modes that will preserve the formant. The formant is the part of the sound that creates the vowel sound, so by selecting one of these other modes it may sound a little bit better for you. The only one of these algorithms that sounds I would say wildly different than all of the rest is Rrreeeaaa. It has a really cool, spacey, reverberant texture to it but it's probably not appropriate for general use.

You can reset the playback rate, you can do that just by typing in 1 and then clicking apply. You can also uncheck Preserve Pitch when changing rate if for whatever reason you wanted to stretch something out and have the pitch shift while you did that.
How to Stretch Audio in Reaper to Adjust Timing

Now I'm going to show you how you can use this idea of stretching an audio item to adjust the timing of a recorded bit of audio. I’m looking at this section of base, above, that I recorded live.
You'll see that the notes are not aligning perfectly to the grid; you don't really need to fuss too much if all of the notes are not 100% on the grid, but at some point in your editing journey, you're probably going to have to clean up the rhythms of something, so let me show you a couple of techniques that you can use to do that.

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Splitting and Shifting

To do this method I like to turn off snapping by pressing Alt S on the keyboard. In this particular case, what I would do is try to get the splits in between the notes as much as possible, I have some space between these first few notes, so if I split it here, you're never going to hear that because the bass isn't really making a lot of noise. When I’ve split it, I can take the audio and just shift it to the left Typically, I like to do that by holding Alt and then left-click and dragging, which is called a slip edit, although Reaper doesn't call it a slip edit.
Sometimes splitting the item and doing a slip edit doesn't always work because there's no space between the notes. In the last six notes of the section, there's not a lot of space between the notes, so it becomes a little bit trickier to try and split this without some weird things happening.
In general when you're doing this technique, you want to have a split to the right of the thing that you are trying to adjust.

For example, if you wanted to adjust this first note here in the selection above, what you would not want to do is take this entire media item and do a slip edit to pull that one note to the left.

What you would want to do is split it here, as shown above, so that everything to the right is unaffected and you can just adjust the one note.

Back to our example and it’s the same deal here, I don't necessarily want to adjust these notes. I only want to work on this one note on the left, so that’s where I put a split, and then I can shift this note over to the left. When I did that, this note should be taking up two 16th notes of time, which the grid is currently set to 16th notes.
Because I played it a little bit loose, that's not really what's happening, but I can fix that by stretching this note just a little bit.

If I just stretch this note where it is, it's going to stretch from the beginning of the media item, which is way over here. That's not going to work for me.

What I want to do is move this split point by holding down shift and then clicking and dragging. I'm going to try and get it as close as I can to the grid without being on top of the grid because I don't want it to be right at the very start of this note because that can sound funny when there's a cross fade that's happening right at the very start of a note.
I can trim this note back just a little.

I'm trimming it back and then stretching it to the right.

That way this note is lasting for the correct amount of time.
A Cleaner Beat

You'd have to really compare that to the original to know that there was an edit made, but now the rhythms are a little bit cleaner. They're happening right on the beat, and it's going to lock in with the rest of the music a bit better. Splitting and slip editing, splitting and stretching is a perfectly valid technique for adjusting the timing that you've recorded audio items.
I'm going to show you one more method that I think you'll find perhaps even more useful. Let's look at using stretch markers to do something very similar
Stretch Markers
Stretch markers allow you to stretch your audio item but not all at the same rate.

I'm going to turn snapping off, and then what I want to do is place a stretch marker at the beginning of each one of these notes by putting my mouse at the beginning of the note and holding Ctrl and Alt on the keyboard, and then clicking. You can see there's a little diamond stretch marker that appeared.

Then I can move along and drop another stretch marker right after. I don't necessarily want to adjust everything in the clip so if I put a stretch marker here and then I move this stretch marker, you can see that it's going to preserve all the audio to the right of the second stretch marker, but I can make an adjustment on the left and move this to the grid.

Really quickly, you can go in and drop stretch markers at the beginning of all of your notes.

If you turn snapping back on, you can snap your stretch markers to the grid, or you can right click on your item, go down to stretch markers, stretch markers in selected items and choose snap to grid and just let Reaper snap everything for you.
It’s similar to the previous method we saw, but it takes a fraction of the time. The reason that I showed you other method is because for some sounds, stretch markers can leave some artefacts behind that may not work. Maybe it's a violin, or maybe it's a female vocal. Using stretch markers might work, but it may be better to split it and stretch it in that more labour-intensive method that I showed you before. Both techniques are totally viable.

There's not a right or a wrong way to do it, just different techniques. I would say most of the time use stretch markers because it's much faster, but if you hear something that sounds a bit off, you may want to undo your stretch markers by right clicking on your item, going down to stretch markers and just remove all of them.
Now you know how to stretch audio in Reaper! In the next lesson we'll look at Reaper effects, or you can go ahead and watch the full free Reaper course now!
About This Page
This page was written by Marie Gardiner from the transcript of a course by David Bode. Dave is an expert on video and audio production. Marie is a writer, author, and photographer. The page was edited by Gonzalo Angulo. Gonzalo is an editor, writer and illustrator.