If you have ever tried to File > Open an Ableton Live Set in Reaper, you already know the answer: nothing happens. Reaper treats .als as an unknown file type and there is no built-in importer that recognises Ableton's project format. The reason is structural, not a missing feature — and it shapes every workaround that exists, including the one this article covers.
This post walks through why the formats are incompatible, what Reaper actually accepts, and the fastest way to bring an Ableton tempo map (with markers and time signatures) into a Reaper project without rebuilding it by hand.
An Ableton Live Set is a gzipped XML file with a custom header. The header declares the Ableton schema version and points at a body of XML that fully describes the project: tracks, clips, automation lanes, tempo map, locators, device chains, every parameter. There is no overlap with the formats Reaper recognises natively — RPP (its own project format), WAV, AIF, FLAC, video files, and standard MIDI files.
Reaper would, in principle, need an Ableton-specific importer. Building one would mean reverse-engineering every ablton schema version, dealing with binary blobs (sample references, device presets), and shipping something that drifts the moment Ableton ships a new version of Live. The Reaper team has chosen to spend that engineering effort on its own format instead — which is fair, given how opinionated Ableton is about its session model.
The real cost: the components that hurt most when you cannot import — the tempo map, the time signature changes, the markers — are exactly the things Reaper does support, but only through specific file formats (MIDI meta-events, in particular). So the path forward is not "force Reaper to read .als." It is "produce a file Reaper does read, and put the same data inside it."
Reaper's tempo and signature handling is built around standard MIDI files. When you drag a .mid file into a Reaper project with the right import option checked, Reaper scans the file for:
If the MIDI file has those events encoded correctly, Reaper applies them to the project timeline the moment you import. If it does not, Reaper imports the file at the project's current tempo and ignores markers entirely.
Before getting to the fast path, it is worth understanding the manual process so you know what the tool is actually doing for you. The hand-built version goes like this:
For a stable session at a fixed tempo with five or six markers, this takes maybe half an hour. For something with twenty tempo changes, five time signature shifts, and forty locators, this is a half-day of careful typing — and any rounding error on the tempo reading ripples downstream into the audio check.
Ableton cannot export a tempo only MIDI file directly, but its .als file already contains the tempo map in machine readable form. The work is in extracting the tempo and time signature events from the XML and writing them out as proper MIDI meta-events.
That parsing step is what Unableton does. Drop your .als file into the converter, get back a .mid file that contains:
The file is a clean Type 0 MIDI file with no note data — it is purely a tempo + signature + marker carrier. Reaper treats it correctly on import.
Once you have the .mid file from Unableton:
.mid file from your file browser into the Reaper arrange window.View > Markers to verify your locators came across with their original names.If your Ableton session has gradual tempo ramps rather than discrete BPM steps, the converter samples the envelope at a high enough resolution to reconstruct the curve as a series of Set Tempo meta-events. Reaper's tempo envelope treats those as discrete changes and renders them as a staircase graph — visually less smooth than Ableton's continuous ramp, but audibly identical because the sample-to-sample delta is below human perception. The audio plays back at the correct tempo at every position; only the editor display looks more "stepped" than you might expect.
Ableton supports time signatures beyond 4/4 — 7/8, 5/4, 11/8, 3/16, and so on. MIDI time signature meta-events encode numerator and denominator as separate bytes, and Reaper reads both. The output is faithful to the source on this front.
Ableton will let you create two locators with the same name at different positions. Reaper's marker system enforces unique names. The converter disambiguates by appending a numeric suffix on duplicate names so you do not lose locators — they all import, just some get suffixed labels.
If your Ableton session has no tempo automation and a single starting tempo, the output MIDI file will contain one Set Tempo event and nothing else. That is fine — Reaper still imports it correctly, and you have just paid the smallest possible conversion cost.
Ableton has shipped .als since Live 4. The XML schema has stayed remarkably stable, and Unableton reads sessions from Live 8, 9, 10, 11, and 12 without issue. Earlier versions are not tested but the schema is close enough that they often work anyway.
Moving tempo maps from Reaper back into Ableton is a different problem — Reaper can export its tempo envelope as a MIDI file with the same meta-events, but Ableton will not auto-import a .mid tempo map in the way Reaper does. The stable round-trip today is one-way, and tools like Unableton exist specifically because the asymmetry hurts in practice.