Backing tracks
Transpose the song.
The track follows.
Attach a backing track to any song in Strofa. When you change the key, the track pitch-shifts in real time — tempo untouched. Shared with the band through the cloud.
Attach and play
One tap to attach. Plays alongside your chart.
Tap the ♪ icon in the song view to attach an audio file — MP3, WAV, M4A or AAC. The file is uploaded to the cloud and linked to that song permanently. From then on, every time you open the song the track is ready without any extra steps.
Hit play and a mini player slides in at the bottom of the screen. You can still scroll the chord sheet while it plays. A scrubber lets you jump to any point in the track — useful for jumping straight to the second verse during rehearsal.
The player shows elapsed and remaining time. Volume is controllable independently of system volume — handy if you're running backing tracks through a DI and need to balance against the acoustic level from the stage.
- Formats: MP3, WAV, M4A, AAC, AIFF
- Mini player visible while reading the chart
- Scrubber for jumping to any position
- Independent volume control
- Track follows when you navigate setlist songs
- Pauses automatically when you close the app
Native Swift module strofa-audioplayer uses AVAudioEngine + AVAudioUnitTimePitch, the same engine as GarageBand and Logic.
Real-time pitch shift
Transpose the song. The track follows automatically.
The pitch engine is a native Swift module (strofa-audioplayer) built specifically for Strofa using AVAudioEngine and AVAudioUnitTimePitch — the same Apple framework that powers GarageBand and Logic Pro. When you change the key in Strofa, the pitch shift value is sent to the native layer and applied in under 50 ms.
Critically, the tempo is not affected. A 120 BPM backing track stays at 120 BPM regardless of pitch shift. You get the pitch you want without the chipmunk effect or the slowed-down result you'd get from a naive speed change. Apple's phase-vocoder time-stretching algorithm handles the trade-off invisibly.
The shift range is ±12 semitones (one full octave in each direction). You can also set a fixed pitch offset per track independent of the song's current key — useful when the recording is in a different key and needs a permanent correction.
Cloud storage
Upload once. Available everywhere.
Backing tracks are stored on secure EU cloud storage. Every band member sees the same tracks without uploading their own copy.
cloud storage, EU-West region. Requires a Strofa subscription. Files stored with your user or band ID — not accessible to anyone else.
Upload to the band library once. All band members can play the track — no need for each person to upload separately.
After the first download, the file is cached on-device. Playback works without internet at the gig.
A track is attached to a song, not a setlist. If the song appears in 5 setlists, all 5 use the same track automatically.
Get started
The track always in the right key.
Free 7-day trial. No credit card required at sign-up.