Press START. Pick a beat and a machine from the menus. Click the labels under the keys to choose which drum you are editing, then click the sixteen keys to change the pattern.
The TR-808, TR-909, TR-727 and LinnDrum each show their own photographed panel; pick one and the window changes. Drag any knob or fader with a red mark. Dead controls are inert on purpose — pans, cassette and sync have no sampler analogue.
The TR-727 is pure Latin percussion — no kick or snare — and the beat still plays via voice fallback. The LinnDrum mixes on vertical faders and pads; it has no sixteen-step row, so edit the beat from the menus above.
The machine menu lists all 443 machines in the library. The four at the top play; the rest are greyed out because their samples are not in this page. The full app plays every one, and exports your loop as WAV or MIDI, which a web page cannot do.