Drum Transient Shaper

A differential-envelope transient shaper in the SPL Transient Designer tradition (Tilgner, 1998). Instead of measuring level against a threshold, it measures the rate of envelope change: a fast peak follower (~1 ms attack) and a slow follower (~15 ms) run in parallel on the mid signal; their normalized difference is positive only while the signal is rising, which is exactly the attack. A second pair of followers — one tracking the natural decay, one with a much slower release that outlasts it — isolates the sustain tail. Attack and sustain gains are therefore independent, level-independent (a ghost note and a rimshot get proportional treatment), and computed per sample. A 5 ms lookahead delay lets the gain curve engage at the very start of each hit. Measured before/after ratios (attack-vs-body and tail-vs-body energy per detected hit) are reported so you can verify the shaping numerically, and a peak guard rescales the output if the boost would clip. Best fed a drum stem or drum bus; on a full mix the tonal balance shifts with the envelope.