The Timbreshiftre

The Timbreshiftre gives you fine tune control over the timbre of a circuit-bent sound.

This a specialized controller that only acts on the waveform data in the ROM. Every other quality of a ROM-bend stays the same. It also has a Crazy Mode..!

It works by manipulating the waveform data of the TONE-presets (ie. Piano, Flute).

The portion of the ROM which exclusively stores waveform data is accessed by the MT-240 CPU on address lines A14 to A17. Normally, those four lines flip bits between 1 and 0 rapidly, as many different addresses in that block are referenced. But when one of these lines is grounded, the address across that line is forced to 0. Different addresses are referenced, the output waveform data changes, and the timbre is tweaked.

What if the ground connection was instead gated by the other (non-waveform) address lines?

It turns out that the other address lines, A0 to A13, follow a pattern. A0 flips bits most rapidly, and A13 least rapidly. If we connect a non-waveform-address-line (eg A0) to the base of an NPN, with the collector to a waveform-address-line (eg A17) and emitter to ground, then every time A0 goes high, A17 is gated to ground.

What does this do to the sound?

This has two effects: 1) We can now choose between many variants of the original timbre. Each combination of the 15 NPNs produces a unique composite of the original waveform and its fully-grounded variant. 2) Another frequency component is added, dependent on the rate of bit flipping of the gating address line. For example, A0 flips the fastest, and thus adds a very high frequency component.

Why six spirals?

Four of them (the three top spirals plus bottom left) control waveform-address-lines A14 to A17, each with their own set of 15 NPNs activated by indiviudal pots. The other bottom two spirals control A12 and A13, which are special- they do access waveform data in the ROM, but not exclusively. They are used more in Crazy Mode...

Crazy Mode?

Instead of gating to ground, Crazy Mode gates address lines to Vdd. This forces the waveform-address-lines to logic 1, and has the (difficult to describe) effect of freezing the timbre into short loops that can stretch and go on crazy glissando runs...

Combining Crazy Mode and Timbre Mode on the Timbreshiftre

A fun way to make full use of the controller is to first freeze a sample in a spiral set to Crazy Mode, then use Timbre Mode on the other spirals. This allows one to change the timbre while it's looping and glissing. You can even use Crazy Mode on multiple spirals simultaneously, which can cause the sound to jumps between textures and timbres as loops freeze and cycle wildly.