Under the Hood: Building a Real-Time Chord Recognizer
Summary
This article details the WhatChord real-time chord recognizer: a four-stage pipeline using pitch-class bitmasks, template-based scoring, normalization, and ranking heuristics. It covers design decisions to avoid ghost roots, how extensions are extracted, and the on-device Dart/Flutter implementation with an emphasis on performance via an LRU cache and efficient bit operations; it also notes open-source licensing and how to report misreads.