Australian company Cycle Instruments have burst onto the scene with a very interesting and highly ambitious debut, the Tetrachords sequencer. A substantial module at 36HP, the Tetrachords promises big: polyphonic sequencing over both CV and MIDI, four sequencer tracks that can work separately or together and bounteous options when it comes to customising scales and chords.

To best understand the Tetrachords’ philosophy, it’s worth taking a closer look at its name. The word ‘Tetrachord’ literally translates to ‘four notes’ and constitutes, for all intents and purposes, half a diatonic scale. Traditionally they’re bound by a perfect fourth — so the first tetrachord of a C major scale, for instance, is C, D, E and F, and the second is G, A, B and C. Of course, when it comes to modular, traditions are there to be broken.

The Tetrachords presents its workflow as two rows of four buttons. Depending on the selected mode — Arp or Chord — these represent notes in a sequence or notes in a chord. Alongside each row of four is an encoder for selecting one of six scales: ostensibly, with both rows set to the same scale and order, and all steps engaged, the Tetrachords will play through that scale from start to finish. I say ‘ostensibly’ because even at this rudimentary stage the Tetrachords starts to open its behaviour up to wildly variable customisation and performance.

Neighbouring Spread and Amount controls for each row can create octave leaps (of multiple octaves, if desired) and dictate the order in which these occur, labelled with little dots and lines and a little white LED meter respectively. A Reverse button switches the direction of travel; since there’s one of these for each tetrachord row, it’s possible to reverse the order of one but not the other. Ordinarily the forward motion of the...