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To your desktop. Press connect MIDI and pick an output. On Windows, create a virtual port with loopMIDI and select it in your DAW; on macOS, enable the IAC Driver in Audio MIDI Setup. Each track sends on its own channel (1–8, change it in the track list) with MIDI clock and start/stop, so drum machines and DAWs follow the tempo. Withfollow clock on, Stochos slaves to incoming clock instead. export .mid writes the whole song as a Standard MIDI File, one track per lane.
The sequencer. Each track has its own length and speed (polymeter), and every step holds velocity, length, chance, a trig condition (1:2, 3:4, FILL, PRE, 1ST…), micro-timing and a CC value. Sixteen patterns; the song is a list of rows with repeats, track mutes, transposition and tempo.
The mathematics. Rhythms from sieves, Xenakis's residue-class algebra (Perspectives of New Music28/1, 1990). Clouds of notes whose density follows a Poisson law and whose pitches follow Gaussian, Cauchy, logistic, exponential or arcsine laws (Formalized Music, ch. I, as in Achorripsis and Pithoprakta). Melodic random walks with elastic barriers (Mikka). Markov chains learnt from your own material, and a song order that wanders by the song's own transition statistics (Analogique A et B). The rotation group of the cube, 24 permutations of the 8 tracks, stepped by Xenakis's recurrence gₙ = gₙ₋₁∘gₙ₋₂ (Nomos Alpha). Cellular automata rewriting a track's gates each loop (Horos). Euclidean rhythms (Toussaint, 2005), the Fibonacci word, and the logistic map (May, Nature 261, 1976). The algebra is checked in scripts/check-stochos.mts.
Transitions. A song row can leave or enter through a transition, or you can fire one live; it starts on the next bar. Fades are linear in decibels (the Weber–Fechner law). Filter sweeps send the track's CC. Builds double their subdivision (1, 2, 4, 8 hits per step). The golden drop falls silent from the golden section of the window, 0.618, to the downbeat (after Lendvai on Bartók). Erosion thins notes with rising probability; the stochastic morph swaps in the next pattern step by step; Fibonacci entries bring tracks in at gaps that grow by Fibonacci numbers; accelerando and ritardando glide the tempo. Each follows a curve: linear, exponential, logistic (Verhulst), sine, or a Brownian bridge, which is new every time.
The stamp says EXP: a single pattern holds 21024 gate configurations, and searching them by brute force takes exponential time. The generators exist so that nobody has to.
After Iannis Xenakis's UPIC, his graph-paper sketches and Formalized Music, and the Elektron sequencer's trig conditions and song mode. Not affiliated with either.