søndag 18. januar 2015


I mentioned in the previous post that I want the synth to be like the Oberheim Matrix line with its software modulation matrix. Here is my take on it: The OMM (open modulation matrix) and its counterpart, the OMMNoM (OMM Node Manager).

The OMM is a piece of firmware running inside the mcu of each voice. It takes a set of inputs, constants, ramps/envelopes and function generators, and through a series of transformations calculates the CVs that control the voice. It is open in the sense that it is possible and easy to add input sources and transformations to the code and it has an open protocol so anything able to generate a simple string stream may be used to create the OMM model.

The OMMNoM is a program used to create the matrix. I envision this as a graphical tool running on a tablet. Through dragging and dropping nodes representing sources and transformations onto a canvas, and then connecting their inputs and outputs to each other and to cv outputs, one creates modulation matrices as advanced as the ones in the Oberheim Matrix line through a much more intuitive user interface.

In the matrix, any output may be connected to any input. Some nodes, such as summing and multiplication accept multiple inputs, while others, for example linear-to-exponential converters and cv outputs only have a single input. All nodes have one output, except the cv outputs which have none (or rather, they have a physical output that connects to the analog part of the voice). An output may of course be connected to any number of inputs.

So far I've thought of the following nodes:

External inputs
- midi controller messages
- keyboard pitch
- keyboard trigger/gate
- pitch bend wheel
- modulation wheel
- physical input switches
- physical input potmeters
- virtual input switches
- virtual input potmeters
- noise input connected to physical noise module of the analog card (use with sample and hold for example).

Controllable functions/function generators
- ramp generators (inc looping?)
- multi stage envelopes (inc looping?)
- LFOs
- Sample and Hold
- Trigger (sends trigger pulse if input is high)
- Comparator - sets output high when one input is higher than the other
- switch - turns on or off a signal when input is high or low)

Mathematical expressions
- sum
- multiply
- divide
- maximum
- minimum
- average
- exponentiation (possibly with dB control)

Logical operators, all with adjustable thresholds (with defaults)
- and
- or
- not
- xor

- CV
- trigger pulse (for analog envelope)
- gate (for analog envelope)
- other binary pins (controlling switches etc)

- numerical constants - these may be entered directly on a node input instead of being a separate node.

The outputs will most likely be named after what they connect to on the analog voice card, but this is not a necessity for the OMM model which just maps the output to a pin or DAC address.

Usage example:

To create an echo with diminishing volume,
an LFO may be connected to the trigger and gate input of an envelope, which in turn is multiplied with a down-sloping ramp. The output from the multiplier should be run through an exponentiation and then connected to the output CV going to the voice's output VCA.

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