Synth Machine

FM synth source page on a FLEX track assigned FMSYNTH.WAV.

A two-operator FM synth machine for FLEX tracks, with one to four paraphonic voices and chords. The voice engine runs on the ColdFire CPU and owns the AMP envelope of a synth track; the DSP shapes and effects the voice as a sample.

Access

Any FLEX track whose sample is named FMSYNTH*.wav becomes a synth. A silent 4 s marker file will do, and the marker's length never ends the note (SYNTH*.wav is still accepted). Not in an official remix; several test remixes carry it. Built from timhastie/octatrick-modules (v2.9) and flashed on its author's Octatrack MKI from 26 Sep 2026.

Operation

• The PLAYBACK page reads PTCH RATO INDX FINE FDBK DEC (title FM SYNTH): PTCH in semitones, FINE in cents.
• On the LFO page, VOIC picks 1 (mono) or 2 to 4 (paraphonic), and CHRD picks one of 32 chord shapes in Syntakt order, each with three inversions on the knob. CHRD can be locked per step, and snaps onto SCALE QUANTIZER's scale and root.
• GLIDE is on the quantizer's row.
• MIDI IN plays a synth track like the CHROMATIC keys: one voice per note up to VOIC, and a note-off releases it.
• A chord fingered on the keys or over MIDI during live recording is recorded as PTCH, CHRD and VOIC locks. Keys within a rolling 150 ms join the chord.
• LEG on every audio track's AMP SETUP page is the legato switch: OFF or MONO on a sample track, OFF, MONO or POLY on a synth track. A FLEX or STATIC track with LEG MONO slides every pitch change over GLIDE.
• In GRID RECORDING, a held trig + FUNC + DOWN or UP moves its PTCH lock an octave.
• ATK, HOLD and REL are read from the AMP page (locks, scenes and LFOs included) and applied in the engine, so a voice is never cut: a re-press continues the sounding oscillator from its level, and a release lasts at least 1 ms.
• A chord's level falls with the square root of VOIC; a 4-note chord is about -10 dBFS.
• FINE reads 0c the moment a track becomes a synth track.
• Known limit: a MACHINE change while a REL INF note sounds leaves it sounding until the next key.

Screen Reference

Synth voice and chord controls on the LFO page.

Status: on hardware: octatrick-usb on his MKI, 26 Sep 2026 (OCTATRICK9) through 2.9; the last two 2.9 fixes under the port.

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