Pstep is a "sample and hold" pattern: The value returned by
next is held at each value in
levels for the corresponding duration in
durs. This cycling is similar to Ptuple, in that the current repeat ends when eiher pattern returns nil.
Pstep measures elapsed time using the thread's logical time. That is, it assumes it will be evaluated only exactly when needed, not before.
Create an instance of Pstep.
A number, collection, or Pattern that returns the levels.
A number, collection, or Pattern that returns segments durations in beats.
An integer, or