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Fills the generator can write
iPhone & iPad · iOS 26.5+
DrumFillGenerator writes strictly linear drum fills — one voice per step, never two — then solves the sticking with a search that refuses to cross your hands, lunge across the kit, or park you on a single drum. Plug in a MIDI kit and every hit you play is measured against the grid to the millisecond. A bank of 200 hand-transcribed fills rides along for the days you want someone else's ideas.
Generator and MIDI tracking are free · No account · No ads · Works offline
What it does
One writes fills your hands can play. The other tells you, to the millisecond, whether you played them.
Every generated fill goes through a dynamic-programming search over your kit's geometry. It costs out hand travel, refuses to cross your right hand under your left, penalises direction reversals, and won't ask for a leap the note spacing can't carry. What comes out is sticking a drummer would actually have written.
One voice per step, never two — the defining constraint of the linear vocabulary, enforced while the pattern is built rather than filtered out afterwards. No limb three times in a row. The kick stays on your foot. The final two steps are never both kicks, so looping never turns your fill into a stutter.
Set the grid and the engine writes to it — 4/4 or 3/4, quarters through triplets, one to four bars, up to 64 sequential steps. Select more than one subdivision and it changes resolution beat by beat. Press again and it writes another. The well does not run dry.
Connect a USB-C MIDI kit and every Note On is timestamped and matched to the grid as you play. Inside 25 ms is a hit, out to 80 ms reads early or late, past that is a miss — green, amber, red, flashing on the step you actually struck.
The reference never moves: scoring is measured against the mathematical grid and deliberately ignores the humanisation applied to playback. Loop a fill, watch your hits drift on the timeline, review each cycle after it ends. Drop the tempo until the whole bar is green, then climb.
A dedicated high-priority audio clock with per-instrument voice pooling, so a fast retrigger never chokes the previous note's tail. Three velocity tiers — accent, body, ghost — per-voice gain control, and a metronome locked to the same clock.
Read the same pattern as a chunky colour-coded step grid with R/L/K sticking, or as a traditional five-line drum staff. Tap any step to cue there, drag to scrub or seek while it plays. Notation is a premium view; the grid is always free.
Four humanisation levels inject micro-timing slop and velocity swing into the audio only — the visuals, the metronome and the tracking grid stay mathematically exact. Change it mid-playback; nothing restarts.
Alongside the generator sits a bank of 200 hand-transcribed linear fills across genres, including ones that switch subdivision mid-bar. Generate presses alternate between the two sources, so at least half of what you get is freshly written. All 200 are free, and the bank updates over the air without an app release.
Wrap the fill in a one-bar prefill/afterfill groove so you hear it the way it lands in a song (premium). Star the fills you want to keep, then rename or delete them in the Favorites tab.
English, Ukrainian, German, Spanish, French, Portuguese, Polish, Czech, Japanese and Simplified Chinese — changed from the app's own settings, independent of your system language.
Generation, playback, notation and tracking run entirely on-device from bundled samples. There is nothing to sign up for and nothing to sign in to.
How it works
Pick 4/4 or 3/4, select one or more subdivisions from quarters to triplets, choose 1–4 bars, and toggle which of the six voices the engine is allowed to use.
The generator builds a linear fill inside exactly those constraints and solves the sticking for your kit. Don't like it? Press again. Every other press pulls from the curated bank instead, so ideas arrive from both directions.
Loop at any tempo with the click on, add the prefill groove for song context, dial in the playback feel, and flip between grid and staff. Tap to cue, drag to scrub.
Connect a MIDI e-kit, enable tracking, and play along. Every hit lands on the timeline against where it should have been, scored to the millisecond, with a per-cycle history waiting when the loop comes round.
Pricing
Premium adds range, not access. Nothing is time-limited and nothing is metered.
No account, no ads, no trial clock.
Auto-renewable, monthly or annual, via the App Store.
Requirements
An engine that writes new ones your hands can actually reach, and a kit that tells you the truth about your timing. On the device already sitting on your music stand.
Get it on the App Store