How to Quantize in REAPER (Audio & MIDI)

Most songs released these days need rigorous edits to land all the transients right ‘on the grid’. When you see this happen at a large scale, it’s natural to wonder if there’s an easier way to get the job done. While the process does require manual effort, there are a few tools related to Quantization that can help optimize the editing process.

quantization reaper

What is Quantization?

Quantization is an editing tool that moves an audio recording, or parts of it, or MIDI notes to the closest grid line. It essentially allows you to transform a less than optimal performance into a time perfect performance, albeit with some limitations.

You can think of it as a coloring book. A messy artist will end up coloring outside of the lines. The same concept applies to playing outside of the beat. What the quantization process does is clean things up, the computer brings everything back in place as it should be. If a take is sloppy, quantization will make it feel tighter. However, using too much of it will take away from the ‘human feel’

quantization grid line

Quantizing audio and MIDI in REAPER involves different tools, so I’ll be exploring the existing methods for both in this article.

quantization reaper 2

Quantizing Audio

In REAPER there are two major ways of editing audio. One is the classic way, splitting/slicing and moving the audio items,and the other is using stretch markers. If you want to know more about stretch markers beforehand, you can take a look at this article.

In order to speed up the editing process further I will be using the Dynamic split function, as it allows you to split items and add stretch markers based on audio transients. I highly recommend that you check the result of the dynamic split before quantizing, but if you want to make the splits or create the stretch markers manually, you can do that as well.

Using Splits

For this example I will show you how to edit a multitrack drum recording to the grid. There have been a few changes to item and track grouping in REAPER v6.72 after I wrote the Dynamic split article that I will take into consideration.

First, let’s start by selecting the tracks and pressing Shift+G to group the tracks’ Media/Razor Edit parameter.

group the tracks’ Media/Razor Edit parameter REAPER

Also, make sure that the option ‘Selecting one grouped item selects group’ in the Action list is set to off.

Selecting one grouped item selects group REAPER

Next select all the kick audio by double clicking the kick track and press D to open the Dynamic split window.

dynamic split window REAPER

Then set up the Dynamic split and Transient detection, the detected transients will appear as vertical green lines along the selected items. In this case use the option Split selected and grouped items.

Split selected and grouped items REAPER

Now, let’s repeat the process with the Snare track so that all the grouped items are split based on the Kick and Snare hits.

group items split REAPER

Here’s where the quantization part comes in. Go to the Item menu, Item processing, and select Quantize items positions to grid.

Quantize items positions to grid REAPER

Once the Quantize item positions window is open, it’s time to set it up. It’s a good idea to quantize the item to the smallest duration note that gets played in the performance, in this case it’s 1/8th notes.

quantize item positions REAPER

Sometimes it’s a good practice to quantize a performance by section batches instead of the whole song.

quantize by section batches REAPER

Then, to cross fade the item junctions, enable Auto-crossfade on your toolbar, then select all items and drag the left side of any item slightly to the left by using the Shift key.

auto cross fade REAPER

If you have the SWS Extensions, you can use the action ‘SWS: Quantize item’s edges to grid (change length)’ instead, which usually results in cleaner item junctions.

SWS Extensions REAPER

If your tracks are in a folder, you can use the phantom waveforms to clean the edits. Also, be careful if the performance is too out of tempo, REAPER may miss-quantize some notes.

Using Stretch Markers

If you prefer using stretch markers, the process is very similar.

Select the Kick and Snare tracks this time. Then, on the Dynamic split items window, use the option Add stretch markers to selected items and grouped items instead of Split.

Add stretch markers to selected items and grouped items REAPER

Then, after having all the stretch markers set up, make sure that all the items are selected and use the action ‘Item: Snap stretch markers to grid’ from the Action list to quantize the stretch markers.

Item: Snap stretch markers to grid

Quantizing MIDI

MIDI quantization in REAPER is a bit more flexible, so let’s check it out.

Quantize dialog

Let’s say that you have a MIDI recording in REAPER and you want to quantize it.

First, double click the MIDI item that contains the notes you want to quantize, this will open the MIDI editor.


Next, select the notes of the section and press Q.

selecting MIDI notes to quantize REAPER

This will open the MIDI Event Quantize dialog. The easiest configuration is quantizing to Grid instead of Manual.

Quantize events 'Use grid' REAPER

Then, you can select if you want to quantize only the Selected notes or Selected events. The second option quantized all MIDI data instead of just the notes.

Quantize events Selected notes REAPER

The Strength slider determines how tight you want to quantize the note positions, 0% means no quantizing, 100% means placing the notes right on the grid. You can quantize only the Position and the Note end too.

quantize events position and note end REAPER

You can check the un-quantized performance with the bypass checkbox before committing to it with the respective button. It’s also a good idea to enable the Fix overlaps option.

bypass, fix overlaps, commit REAPER quantize events

All that’s left is clicking OK.

Quantize on Input

Now, there are occasions where it’s more convenient to quantize a MIDI performance right as you’re recording it. This way, you don’t have to open the MIDI editor to quantize the performance each time you stop recording. Input quantization is especially useful for quickly recording ideas, or recording my layers like you would for live looping.

In REAPER, the Input quantize option is enabled on a per track basis. To open it, right click the rec arm button of the track where you want to record the MIDI performance, and select the option Track recording settings.

Track recording settings REAPER

Once the Track recording settings are open, enable the option Quantize track MIDI recording.

Quantize track MIDI recording REAPER

Here you can set up to what size of grid you want to quantize your MIDI performance, that will depend on the time signature and the smallest subdivisions of your performance, in this case it’s 1/4 notes.

size of grid you want to quantize your MIDI performance REAPER

Letting Positioning on the default option, Nearest value is the most versatile. Aside from the Strength slider, you can also quantize to a Swing grid that is very common in jazz related genres.

strength swing quantize within REAPER

The Quantize within sliders allow you to leave some notes untouched depending on how far or close they are to the grid, the default positions quantize all notes.

quantize within sliders

Once you set it up, every MIDI performance you record in this track will be quantized automatically.

auto quantize post setup REAPER

The quantization can also be undone by opening the item in the MIDI editor.

undo quantize REAPER

Select all the notes, press Q and Bypass the quantization.

Final Words

Audio and MIDI Quantizing are one of the best tools you can have in your arsenal to speed up your workflow. If you learn to use it well, it can literally save you days of editing in the long run. I dare you to try different configurations and integrate it into your workflow. Also, take a look at other REAPER tips and tricks in the REAPER article section. Happy editing!

Jose M.
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