If you're looking for guitar-chord detection in particular, I'd recommend you take a look at Chordify ( ). I.e., is it sufficient to say "that's a C Major chord" or are you looking for a specific inversion or even fingering? Does it need to happen in real-time based off a microphone or could you batch-process an audio file instead?īut there are both academic solutions and consumer-oriented tools that can do a reasonable job of it (again, depending on what you're looking for). The polyphonic case (like chord detection) is trickier, especially depending on what you're looking for exactly. Even naive solution like just counting the number of zero-crossings in the audio signal to estimate the fundamental frequency works pretty well. The monophonic case (one note at a time) is fairly well solved at this point: there are decades old solutions in both the frequency domain (like FFT) and time domain (like auto-correlation and the dozens of refinements of that basic concept) that work quite well under less than ideal conditions and in near real-time.
) but I would suggest that it's still good enough to be useful - and I encourage the parent to continue their work, as it's an interesting area to explore.Īutomated music transcription - the process of generating a musical score from an audio recording - is a pretty active topic in signal processing (and has been for a couple of decades at least). these MIREX evaluation results from 2018 which compare Chordino with a few other academic methods. This type of method is now routinely outperformed by neural networks (see e.g. Some sort of intelligent smoothing like this is certainly needed, the raw template matching is not especially useful on its own. There is a reference describing the Chordino method in the page linked above, but roughly it's not too far from the description of the parent poster - a non-negative least-squares method produces a frame-by-frame semitone-scaled decomposition which is then matched against templates and turned into a chord sequence using a hidden Markov model.
There are various commercial offerings that do this, including Chordify and Capo.Īlternatively if you want a flexible free (GPLv2) option with source code, consider the Chordino plugin (, C++ code at ) which you can run in Sonic Visualiser ( ), or indeed in Audacity.
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