I watched both supply rails, they're solid. I tried smaller values but that didn't fix the problem and actually caused some attenuation on the input bad enough to negatively affect other parts of the circuit.
The pulse is coming from some DAC I don't recognize, into the common pin of a HD4051 MUX, then depending on which key/trigger is selected it gets connected to one of 8 RC circuits which create a decaying exponential with a time constant of about 200ms and peak voltage of 3.1V. That signal then goes to the base of a npn transistor which acts as a gate for an audio sample. The frequency depends on user inputs/stored patterns, nothing over a few Hz though. Mostly just testing with oneshots.
I'm wiring into the RC networks just in front of the npn bases. Running lines from there to my amplifiers and then to a patch bay for connecting other devices.