The curiously named debut iPad app from synth design legend Wolfram Franke is a virtual groovebox complete with step sequencing, effects, copious modulation options, AudioBus and WIST support, and a sizeable library of bundled samples and presets, including contributions from Oberheim (a collection of DX and DMX samples) and Back In Time Records.
Stroke Machine can host 12 drum sounds and 12 melodic (playable up and down the keyboard) sounds at once. Each one is generated by a two-oscillator analogue-style synth with sine (featuring Asymmetry, Slope and Saturation controls), triangle, pulse (width-adjustable) and saw waves available to it, as well as sample loading.
FM and ring modulation can be applied, and the filtered white/pink noise oscillator can be used to bring FM to bear on Osc 2. The Transient Generator ices the cake, packing five modules (Crack, Rattle, etc) with which to add some front to your drum sounds, while the filter offers a range of modes (LP, HP, BP and BS, from 6-24dB/octave) and sounds fantastic.
Modulation-wise, you get two envelopes, an LFO and four randomisers, all easily assignable to as many targets as you like, with targets taking input from as many mod sources as you like. Note pitch and velocity can be used as mod sources, too, and automation of all parameters can also be recorded manually. It's a powerful setup, but persistent indication of mod routings is needed.
The synth engine has analogue and digital distortion effects onboard, and EQ, while four auxiliary send buses each house four effects, including dynamics, distortion, filtering, delay and reverb.
The sequencer, meanwhile, enables up to 128 patterns to be strung together into "performances", each pattern up to eight bars long and loading its own associated soundset.
Stroke Machine's eye-wateringly neon interface crams a lot of controls into its various tabbed pages and is quite fiddly because of it. It's also a bit buggy in its current state.
That's where the criticism ends, though, as this is one of the best virtual studios on the App Store, successfully combining synthesis, sampling and sequencing in a package that serves a genuinely productive role both in the studio and on stage.