Map the tempo

The Tempo page builds a tempo map that follows the recording, so REAPER’s bars and beats line up with what the band played. Chords can then snap to bars.

It needs the Beat detection component. If the page shows Install, click it, or see Add the tools you need.

Detect and map in one go

1. Select the song’s audio item.
2. Open the Tempo page and click Detect beats.

Expected result: the song’s part of the project gets a tempo marker on every beat, in one undo step. A bar before the song’s first downbeat becomes its count-in. Nothing that plays moves in time: the song, its stems, the chord and lyrics tracks, your markers, regions, and automation stay where they are and follow the new bars from there.

If there is no room for the count-in before the song, PresTools inserts the time it lacks where the song’s audio begins. The song and everything after it move later, together.

The button becomes Detect again once there are beat markers.

Songs in 6/8 and other eighth-note signatures

PresTools 0.1.0 writes the tempo map of a song in an eighth-note time signature, such as 6/8, at the wrong BPM, so its bars don’t match the beat markers. This is fixed in the newer PresTools built into Prest, and comes to REAPER with PresTools’ next release.

Check the beats before you map

1. Untick Build the tempo map.
2. Click Detect beats.

Expected result: each beat is a project marker, and nothing else changes. The first downbeat, and any change of time signature after it, is named with the signature, such as [4/4], and shows red. The other beats are green.

• Click track puts a click on every marker, accented on each downbeat, on a new track named Tempo preview. Play it against the song. REAPER’s own metronome follows the tempo map, which is not written yet, so it can’t do this job.
• Remove clicks deletes the Tempo preview track. Applying anything removes it too.
• Apply markers builds the tempo map from the markers, with the count-in, in one undo step. It uses up the beat markers it read.

Correct the markers

Move, delete, or add markers with REAPER’s own marker tools, or use the buttons under Edit markers. Each button is one undo step, and none of them changes the tempo map until you apply.

Button	Does
Halve	Keeps every other marker, in the time selection or the whole song. Use it when the beats came out at double the tempo.
Double	Puts a beat in every gap, in the time selection or the whole song. Use it when the beats came out at half the tempo.
Fill the gap	Spreads the number of beats you type across the gap the edit cursor is in.
Set on the nearest marker	Starts a bar, in the time signature you type (such as 3/4 or 6/8), at the marker nearest the edit cursor.

You can also type instructions into a marker’s name. A marker with an ordinary name and no square brackets is yours: PresTools never touches it.

Marker name	Means
(no name)	A beat.
[4/4]	A time signature. The first one marks the first downbeat; anything before it is a pickup.
[7/8]	Any signature works. Write one only where it changes.
[skip:2]	From here on, use every second marker. A new signature resets it.
[fill:4]	Fill the gap to the next marker with 4 evenly spaced beats.
[fill:3x4]	Fill each of the next 3 gaps with 4 beats.
Verse [4/4]	A named marker can carry an instruction too; the name is kept.

When markers hold fill or skip, the button reads Expand markers: it writes them out as ordinary beat markers and does nothing else. Click Apply markers after that to build the map.

If a marker can’t be read, such as [5/9], the page says A marker cannot be read and what is wrong. Fix it before you apply.

Correct a finished map

With no beat markers in the project, Map to markers reads the tempo map back as one beat marker per beat, across the selected item, or across the whole project with nothing selected. Correct them, then apply again. The map is only ever rewritten from markers, never edited in place.

More than one song in a project

A song later in the project keeps the map of the songs before it. Its bars start from the last bar line before it that leaves room for its count-in.

Tick First song’s count-in in bar 1 to lay the first song out from the top of the project instead: bar 1 is its count-in, and its first downbeat is bar 2. The song and everything after it move to meet them. Songs after the first are not affected.

Detection settings

Detection settings (the sliders button in the page’s header) opens these. Defaults puts them back.

Setting	Default	Change it when
Min BPM	55	The beats come out at half the tempo: raise it (for example to 100).
Max BPM	215	The beats come out at double the tempo: lower it (for example to 140).
Tempo stability	250	100 follows the performance closely; 400 holds one tempo.
Beat sharpness	24	The beats land between the played ones, half a beat late: raise it.
Time signatures	4	The song isn’t all in 4: list the beats per bar it may choose from, such as 3 4 to allow waltz bars.

Detection runs on the GPU unless you turn it off in Settings. If the GPU can’t run it, it finishes on the CPU. The first detection downloads the detector’s weights.

Next: Find chords.