Tag Archives: number set

Adjust pitches according to a pitch class set

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One potential use of the “inlist” abstraction is to compare incoming pitches to a pitch class set. This patch uses a % 12 object to find the pitch class of an incoming pitch, then compares it with the members of a prescribed pitch class set. If it belongs to the pitch class set, it gets passed on unchanged; if it doesn’t belong to the pitch class set, it gets pushed up one semitone and tested again.

Note that this patch does point to a potential bug (a so-called “screw case”). If the pitch class set is null (the bag inside the inlist abstraction is empty), any incoming pitch would set this patch into an infinite loop and cause a stack overflow. However, we’re safe in this particular example because we have pre-loaded the pitch class set and there’s no way provided in the program to delete those numbers.

Ask if a number belongs to a set

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This abstraction, which I call “inlist”, checks to see if a given number belongs to a previously-collected set of numbers. Numbers in the middle inlet are added to the set, and numbers in right inlet are deleted from the set. A ‘clear’ message in the left inlet deletes the entire set. When a number comes in the left inlet, if it belongs to the set, a 1 will be sent out the outlet, meaning “yes, it’s in the list”; if it doesn’t belong to the set, a 0 will be sent out.

The bag object stores an unordered collection of numbers. Each time a number comes in the left inlet, we store it, then compare it with every number in the bag, storing any “yes” answer we may get. Then we send out the stored answer and reset the stored answer to “no”. (N.B. Technically, we really reset the stored answer before we send out the result, so that “inlist” will be all ready to go even if its output triggers more input in the parent patch. The answer actually gets to the final t object and is stored there for an instant while we reset the i object to 0.)