The minim Library is popular - http://code.compartmental.net/tools/minim/quickstart/
If you haven’t used it already.
Daniel Shiffman has a tutorial playlist on sound using p5js - https://www.youtube.com/playlist?list=PLRqwX-V7Uu6aFcVjlDAkkGIixw70s7jpW
can you go over in more detail about your algorithm or show us some working code examples to help simplify your process?