ugen builder too difficult to reason about wrt caching and rollbacks.
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clarify the identity of views
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basic new-aural-test ok. have commented out all the routine stuff, yet
clean up
new aural-scan approach
ok, but now we have one aural-scan per scan; that means it needs to
handle multiple proc-auralnodes
start to say good-bye to auralnode
further abstract from aural-node (node-ref)
mas
getting messy again
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here's a test case that should be correctly handled (sound)
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step
step
do away with the time arguments for now; they should come back in the
  form of an additional context implicit