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+Feature ideas (beyond the four-pots, CV in, CV out basic ADSR):
+
+- CV control over each phase
+- Gate/trigger out for each phase
+- manual gate (simple debounced button should do)
+- retriggering (present in Kassu and descendents)
+- looping (present in Kassu and descendents)
+- inverting (trivial in any design)
+
+The 555 approach is classic, been around since the 80s, maybe earlier.  However, I haven't found a 555 design (yet) that makes use of phase CV.
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