Pre-rendered audio analysis APIs supply timestamped beats and pitch for offline sync

Instead of computing FFT or onset detection in real time, a track can be analyzed offline by a service (formerly Echo Nest, now the Spotify Audio Analysis API) that returns timestamped beat, bar, tatum, pitch-segment, and loudness data as JSON. The visualizer syncs a playback cursor to those timestamps, triggering visual events at known musical moments. This offloads DSP complexity, gives access to higher-level musical structure (sections, bars, beats, tatums), and produces more musically coherent animations — but it requires pre-processing and an internet-accessible API, and does not work for live or unknown audio.

Examples

Echo Nest Beat + Pitch demo: load JSON with beat timestamps, map each beat to a visual event; contrast with the real-time p5.FFT approach where beat timing is inferred from amplitude peaks.

Assessment

List two advantages and two disadvantages of pre-rendered API analysis vs. real-time DSP for a music visualizer; name the musical time units the Echo Nest/Spotify API provides.