The ComboBox plug-in was added in Unify v1.2.0. Unlike all the other plug-ins bundled with Unify, it neither produces or processes either sound or MIDI by itself, but instead provides an environment in which you can connect any number of plug-in instances in arbitrary ways, and thus escape the constraints of Unify's linear-chain layer architecture. It's also unique in that you can use a ComboBox instance in any of Unify's three types of plug-in slots: Instrument, MIDI-effect, and Audio-effect. (MIDI Monitor is the only other plug-in which can sensibly be used in all three slot types.)

The image above shows a fairly simple ComboBox patch, taken from the first INST layer of the “Arrival - 0 - Welcome to Unify!” patch in the Unify Standard Library.

• The three boxes labeled “Audio File Player 1”, “Guru Sampler 2”, and “mda Vocoder 1” each represent plug-in instances.
• The two boxes labeled “MIDI Input” and “Audio Output” do not represent plug-ins, but rather the inputs and outputs of ComboBox itself.
• The colored lines represent connections, red for MIDI, green for audio. The arrows indicate the direction in which the MIDI or audio flows.
• The boxes (of any kind) are called nodes, and the entire structure of nodes and connections is called a graph (a mathematical term; see https://en.wikipedia.org/wiki/Directed_acyclic_graph).
• The keyhole-shaped bumps where connections begin and end are called pins (by analogy to connector pins in electronics).

In this particular graph, the input MIDI stream is sent to the MIDI inputs of the Audio File Player and Guru Sampler. Each of those nodes has two audio outputs, representing the Left and Right stereo channels. One of the most important things about ComboBox is that it allows you to connect each plug-in's Left and Right outputs (or inputs) individually, and make multiple connections to a single pin (as is the case with the MIDI input here). Contrast this with Unify's layers, where plug-ins are always connected in daisy-chain fashion, and all audio connections are stereo.

The ability to connect Left and Right pins in different ways is absolutely critical for the mda Vocoder, whose Left input takes the Modulator signal and the Right takes the Carrier signal. The vocoder impresses the dynamic tone of the Modulator (in this case a short vocal sample played by an Audio File Player) onto the Carrier (in this case, musical notes/chords played by a Guru Sampler using a synthesized pad sound). The mda Vocoder is actually a mono effect, so its Left and Right outputs are exactly the same.

When the state of a ComboBox is saved within a Unify patch, the state-data includes

• The list of nodes, their names, and their X-Y position coordinates in the display
• The name and type of plug-in used for each node (except input/output nodes)
• The state-date for each plug-in

This information is sufficient for Unify to completely restore the ComboBox instance to the state it was in when the patch was saved.

When you first load an instance of ComboBox, it will look like this:

Work in progress… TO BE CONTINUED…

• Right-click in background area to add new plug-in instance nodes
  • Unify assigns node-names automatically by adding “1”, “2”, “3”, etc. to the plug-in name
• Double-click in any plug-in node to open that plug-in's GUI in a separate window
• Right-click in any node for a menu of operations
  • Including removing the node (and all its connections) from the graph
  • You can safely remove any input/output nodes you don't need (you can add them back later)
• Plug-ins which have more than one stereo output-bus (Left and Right) will be drawn using a different pin color for each bus.
• Create connections by left-clicking any output pin and dragging to any input pin of the same type (MIDI/audio)
  • You can also drag in the other direction (from an input to an output)
  • You can connect one output to several inputs; this is called a split. The output data are simply copied to all inputs, without change.
  • You can also connect several outputs to one input; this is called a merge. Merging MIDI streams yields one combined MIDI stream. Merging two or more audio streams is basically the same as mixing them; the audio samples are simply summed.