music21 vs Open Music Theory

music21 is a free Python toolkit for computer-aided musicology, used to study music datasets, teach music theory, edit notation, analyze music, generate examples, and compose. It includes a corpus of thousands of encoded works, plus tools for searching that corpus, plotting pitch, and performing advanced analysis such as nPVI. The toolkit works with MIDI and MusicXML and can be extended to handle other formats. Its documentation recommends MuseScore for viewing and editing notation, and describes MusicXML readers including Finale, Sibelius, and Dorico. Optional integrations include LilyPond, Matplotlib, SciPy, PyAudio, and Pygame; music21 can also be used in web-based Jupyter Notebook. It runs on Linux, macOS, and Windows, with web use through Jupyter. The toolkit is BSD-licensed and costs nothing. Some corpus works have separate license restrictions. Users need some familiarity with Python, and music21 works primarily with symbolic music data rather than sound waves; it cannot read notation directly from images or PDFs.

Open Music Theory has no write-up on Specifiction yet; its figures are above.