A hi-hat is synthesized as white noise passed through a high-pass filter with a fast decay envelope

The tonal content of a closed hi-hat is broadband noise heavily weighted toward high frequencies — cymbals are metal plates with complex inharmonic spectra that resemble noise more than pitched tones. The simplest synthesis approximation is: white noise oscillator → steep high-pass filter (e.g. 24 dB/oct) → fast-decaying amplitude envelope in trigger mode. Filter cutoff determines brightness (open vs. closed character); envelope decay controls whether it sounds closed (tight) or open (lingering). For open hi-hat, the envelope decay is longer and the trigger/gate mode distinction matters: normal mode allows the note length to control decay, which is useful for live playing of open/closed hat pairs.

Examples

Operator: noise white oscillator → 24 dB highpass at ~8 kHz → trigger mode with ~60 ms decay = closed hat. Switching to normal mode and holding the note longer = open hat.

Assessment

Describe two synthesis parameters that distinguish a closed hi-hat from an open hi-hat in this patch. Then explain why the 24 dB highpass slope is preferable to a 12 dB slope for this application.