This homework assignment is designed to give you practice making a voice bank using abstractions. The assignment is to make a 4-voice polyphonic synthesizer. To keep things simple, the "voices" can just be sinusoids with amplitudes controlled with line~ objects. The synthesizer should play "notes" passed as messages; in this case, the patch should generate notes from a probability distribution (another technique we haven't used yet).

Your successful patch should be able to make sounds like this.

To make the patch (each of the following steps is worth 2 points for a total of 10):

• Make two patches, a main patch and an abstraction that you could call, for instance, "voice.pd". Put these in a new folder with a unique name (name it for yourself for instance). To upload the assignment, you'll make a zip archive of the folder with the two files in it; this is the way you should upload assignments from now on.
• Inside the "voice" abstraction, make a patch that multiplies an oscillator (with a controllable pitch in MIDI units) by a line~. There should be an input for messages to play a note (which should contain at least the pitch to play). There should be an output for the audio signal. These can both be managed via inlets and outlets. The most sophisticated way to manage the audio output is to have both a signal inlet and outlet, so that you can daisy-chain the copies, each adding itself to the sum of all the previous ones.
• Inside your main patch, using "metro" and "array random" objects, create a random stream of pitches, preferably somewhere between 60 and 120 (so that the sinusoidal sounds made by "voice" sound reasonably good.) You can use "+" to add an offset such as 60 to the output of "array random". You can invent your own collection of pitches to put in the array or just use mine (0 5 7 10 12 15 16 19 22 26). NOTE: don't just put those values in the array; put "1" at those locations and leave the rest at "0".)
• Place 4 or more copies of the abstraction inside your main patch, and make a counter (ranging from 0 to 3, for instance) to choose which copy of the abstraction to send the message to. You'll have to pack the counter output with the pitch you computed earlier, and "route" to then route the messages to one of the 4 (or more) abstraction copies.
• After summing the signal outputs from the abstractions, make an overall amplitude control to turn the patch output on and off. There should also be controls to turn the "metro" object on and off, and a control for its speed (controlled by changing the "metro" time in milliseconds). When you load the patch, it should start making sound once the amplitude control and the "metro" are turned on.

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