01
The pairing you keep describing to people
Two songs you've always thought would fit, and no way to prove it. Upload both and play them the actual thing instead of explaining it again.
Blend two songs
Add two tracks. We work out the tempo and key match for you.
sings
Drop a track here
MP3 / WAV / FLAC / M4A · max 50 MB · 10 min
plays the backing
Drop a track here
MP3 / WAV / FLAC / M4A · max 50 MB · 10 min
We check the tempo gap, the key distance and whether both tracks have a steady beat before rendering. If a pair won't work, your credits come straight back.
Results
Play it back, adjust the balance, then download.
One song's vocal. Another song's beat.
Pick two tracks and we separate the vocal from one, the instrumental from the other, then line them up on the same tempo, key and bar grid. If they don't fit, we say so instead of handing you something that sounds broken.
How it works
Four steps, no timeline to learn
The whole thing is automatic. The only decision you make is which track sings.
1Step 1
Add two tracks
Upload files, pick from songs you've generated here, or reuse a split you already ran through the stem splitter.
2Step 2
We read both songs
Tempo, key, beat positions and section structure — measured on the original mixes, not the separated parts, because a bare vocal has no reliable beat to track.
3Step 3
We check they fit
Too far apart in tempo or key, or no steady beat to lock onto, and we stop and refund rather than hand you something that sounds broken.
4Step 4
Listen and adjust
Play the result against either original, then nudge the vocal and backing levels or shift the timing by a fraction of a beat.
What makes it line up
The parts that decide whether a mashup works
None of this is exposed as knobs. It's here because it's the difference between a mashup and two songs playing at once.
Bar lines, not just beats
Beat tracking tells you where every beat is, but not which one starts the bar. Land the vocal on beat three and the whole thing collapses. We vote on beat energy to find the downbeat before anything gets aligned.
Tempo read at the right octave
70 BPM and 140 BPM are the same groove counted differently. We normalise for that before measuring the gap, so a compatible pair doesn't get rejected for being '100% apart'.
Relative keys understood
A minor and C major use the same notes. Treating them as three semitones apart would mean shifting a backing track that already fits.
Chorus onto chorus
When both songs have a readable structure, the loudest, most repeated sections get matched to each other. When they don't, we say so and run the backing straight through instead.
Vocals stay untouched
Pitch shifting is applied to the backing track wherever possible — listeners know the original singer's voice, and that's the part you notice being processed.
A limit on how far we'll stretch
Time stretching smears percussion. We keep it inside a range where it stays acceptable, and refuse the job rather than quietly shipping mush.
Who it's for
Made for people who already hear the pairing
The steps are the same for everyone. What changes is why you wanted those two songs on top of each other.
02
Short-form video
An audio bed that's recognisable in the first bar but isn't the same version already sitting under a thousand other clips.
03
DJ sets and party playlists
A transition that only exists on your laptop, already matched in tempo and key. Download it at 320 kbps and drop it into the set.
04
Producers testing an idea
Find out whether a pairing is worth an afternoon in a DAW before you spend one. If it holds up, split both tracks and rebuild it properly.
Pricing
60 credits per mashup
That covers two separate AI separations — one for the vocal, one for the backing — plus the analysis and the rendering. Bring a track you already split here and that side is taken off the price.
Refunded when we refuse
If the two tracks turn out to be incompatible, the credits go straight back to your balance. You only pay for mashups we actually make.
Re-balancing is free
We keep the separated vocal and backing, so changing the levels or nudging the timing re-renders without charging again.
No watermark
The download is the finished mashup at 320 kbps. Nothing is stamped over it and nothing is held back for a higher tier.
FAQ
Questions
One song's vocal over another song's instrumental, matched in tempo and key. It is not two songs playing at once, and it is not an AI writing a new song that sounds like both — you hear the actual recordings you put in.
No. You upload the audio yourself, or pick from songs you've generated on Lacuna.
One of three checks failed: the tempo gap was wide enough that stretching would audibly smear the drums, the keys were too far apart to shift without the backing sounding wrong, or one track had no steady beat to lock onto. The result page says which one, and your credits are refunded.
Whichever vocal you want to hear. By default the shorter song sings, because the backing track is the side that gets trimmed or looped and the longer one has more material to work with. You can swap it before you start.
No, but closer is better. Under about 6% apart and you won't hear the stretch at all. Past 12% we stop, because time stretching that far makes drums sound washed out.
We shift the backing track to match the vocal. Up to three semitones that's clean. Beyond that we move the vocal instead, using a method that preserves vocal timbre. More than five semitones apart and we stop.
No — this tool goes straight to a finished mashup. You get level control for both parts and a timing nudge. If you want multitrack editing, split the tracks with the stem splitter and take the parts into your own DAW.
Usually three to five minutes. Most of that is the two AI separations; the analysis and the actual blending are fast.
Related tools
The rest of the chain
Try a pair you've always wanted to hear together
Two tracks, four steps, and an honest answer when they don't fit.