Sozo has two halves with very different reach, and it's worth knowing which is which.
The analysis is done by omsanalyze, which uses Apple's Music Understanding framework. That framework is part of the operating system (macOS 26+ / iOS 26+), so producing the JSON sidecar for a track requires an Apple device on a supported OS. There is no cross-platform or cloud version — Apple's analysis only runs on Apple's OS.
The visualizer — this app — only reads that JSON. Once a sidecar exists, it plays back in any modern browser on any operating system. Nothing Apple-specific is needed to view or perform an analysis.
To analyze a track: a Mac or iPhone/iPad running macOS 26+ / iOS 26+, plus the omsanalyze CLI. Run it once per track — it writes a portable JSON sidecar.
To view / perform: any modern browser (Chrome recommended), any OS. Load the sidecar and the audio and press play.
Not in the browser. Music Understanding isn't reachable from JavaScript on any platform — not even Safari on a Mac — so the app can't take an arbitrary MP3 and analyze it in-page. It reads analysis that was produced ahead of time by omsanalyze on an Apple device.
The upside: the Apple-only step happens once, offline, and its result ships as open, portable JSON that everyone else can use forever. The analysis gets freed from the OS the moment it's serialized.
Full setup, the omsanalyze source, the JSON schema, and developer notes ship in the project bundle alongside this app. See the included documentation for the technical details.
OMS Sozo is a visualizer for the Apple Music Understanding framework. You analyze a track once with the companion omsanalyze CLI, which produces a JSON sidecar, then load that sidecar and the audio here to see — and hear — exactly what Apple's analysis found.
The timeline lays the analysis over a real waveform: the bar grid, beats, and the nested structure of sections, segments, and phrases, plus key and loudness. Press play and the playhead sweeps the grid so you can confirm, by ear, that the markers land where the music actually does.
Music Understanding is an Apple framework (macOS 27 / iOS 27) that analyzes audio entirely on-device and returns six time-aligned dimensions: rhythm (beats, bars, BPM), key (as ranges that can change across a track), structure (sections / segments / phrases), loudness (LUFS), pace, and instrument activity — all as a single SessionResult.
What makes it notable isn't that key or tempo detection exists — it's that all six dimensions come from one on-device call, free, bound to no product, as portable data you can build anything on. The hierarchical structure (sections → segments → phrases as timed ranges) and time-ranged key are things existing DJ tools don't expose as open data. That composite is the point.
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• 500+ releases | 7,000+ days in Beatport charts
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