You may have seen my tutorials on creating grooves with EZDrummer and creating custom drum tracks with Jamstix 2. These are great when creating a song recording from scratch, but what if you have an existing recording to add drums for? What about taking any existing recording and adding some midi synths to spruce up your production? I'm going to show you how to use REAPER to take any home recording and tempo map it so you can add custom drums or midi elements after the fact, and have them be in perfect sync with your audio tracks.

Custom shortcut keys in REAPER

The first thing we will need is to create a custom keyboard shortcut in REAPER. You can create keyboard commands to do simple or complex sequences of commands. From the Tools menu choose Preferences (at the bottom). Then on the left of the preferences window, choose Keyboard/Control and you will see a list of keyboard shortcuts. Click the button labeled New… to create our custom shortcut and configure it as shown:

reaper tempo mapping shortcut

I chose Ctrl+Shift+X as the shortcut so it would be easy to press with one hand. You can use any combination you would like, but this tutorial will assume it is set up as Ctrl+Shift+X.

Another option of interest to us is the horizontal zoom behavior of our DAW. Still on the preferences window, click the Editing Behavior category on the left. Look at the setting for Horizontal zoom center with a dropdown box next to it. I like to have this set on the default of Edit cursor or play cursor and the technique in this tutorial will rely on this behavior.

Pick a timekeeper audio track

It is essential to pick one of your audio tracks to be the master timekeeper track. We will consider this track to be the authority on where the downbeat is at any given time. Often this will be the drums, sometimes it might be the bass, but it could be any element of the mix. Just be sure to pick the instrument that you consider to most consistently represent the true tempo of your song. For this article I will be tempo mapping a straightforward blues rock number with a solid drummer. So I'm going to use the snare and kick drum as my timekeeper tracks.

Start placing tempo markers

With your timekeeper track chosen and shortcut key created, it is time to start dropping tempo markers!

General Note: The accuracy of your tempo map is determined by the accuracy of your tempo markers. You can zoom in really far to place very accurate markers or stay zoomed out a bit to allow them to be a little less accurate. Do whatever feels best for your project. I generally zoom in pretty far.

Rewind by pressing the Home key on your keyboard, the W key on your keyboard, or the rewind button on the REAPER transport. This will put the cursor at the start of your project. Zoom your view so you can see the first downbeat of your timekeeper track. For me this is the first drum stick of a four beat count in.

Position your mouse over the start of the first beat but DO NOT CLICK IT! Instead, press your Ctrl+Alt+X shortcut key. You will end up with something resembling this next screenshot.

reaper tempo mouse position 2

The highlighted region is a time selection that was created and two tempo markers have been created. Notice they are shown as being over 712 beats per minute! Don't worry too much about that breakneck tempo, we're about to fix that. Zoom and reposition your window so you can see the downbeat of the next bar. Be very cautious not to click on the window and move the playback cursor. Here is the first kick drum beat of my song.

reaper tempo mouse position 3

After positioning my mouse as shown, I press my shortcut key again to define the first measure of my song. As you can see, the count in is at just about 123 beats per minute.

reaper tempo mouse position 4

An important thing to keep in mind is the last shown tempo marker is not correct. Everything other than the last marker is correct. Continue in this fashion, positioning the mouse over each downbeat and pressing your shortcut key. Soon you will see your new tempo map taking shape. Keep doing this until you have gone through your whole song, marking the beginning of each measure.

reaper tempo map

Notice the count in was at 123 beats per minute while the song kicked in at about 131 bpm. The tempo also appears to shift on every bar but this is normal for music played by actual humans.

Tempo map!

Once you have gone through your entire song it will be easy to make edits on downbeats to splice sections together, add midi drum tracks (or synths), and generally do anything you could do with a midi production or song that was recorded to a click track in your home studio.

Tip: If you lose your place or accidentally move the playback cursor you can get back on track by clicking directly on the [T] marker for the last tempo in your track.