Browser-native audio analysis for JavaScript — BPM & beat tracking, spectral features, structural segmentation, and intelligent loop detection. Zero dependencies. TypeScript declarations included.

pleco-xa brings musical intelligence to anything that runs JavaScript — the browser, Node, Web Workers, the edge. Tempo and beat tracking; mel / MFCC / chroma / spectral descriptors; structural segmentation; DTW & sequence alignment; effects; pitch tracking; pure-DSP vocal separation; and its signature loop detection — with zero runtime dependencies and no build step required. 47 CI-gated test suites (420 tests) run on every PR and push to main, with loop detection locked against committed golden fixtures on real audio.

Install

npm install pleco-xa

Two ways to import

The barrel — everything, tree-shakeable:

import { beat_track, loop, stft, feature } from 'pleco-xa'

Per-namespace subpaths — pull only the domain you need:

import { mfcc, chroma_stft, spectral_centroid } from 'pleco-xa/feature'
import { detect } from 'pleco-xa/loop'
import { hz_to_note, hz_to_midi } from 'pleco-xa/convert'
import { dtw, viterbi } from 'pleco-xa/sequence'

TypeScript declarations ship for the barrel and all 19 subpaths — editor autocomplete works out of the box, no @types/… package needed.

Quickstart

import { beat_track, loop } from 'pleco-xa'

const ctx = new AudioContext()
const audio = await ctx.decodeAudioData(await (await fetch('song.mp3')).arrayBuffer())
const y = audio.getChannelData(0)

const { tempo, beats } = beat_track(y, audio.sampleRate)
const best = await loop.detect(audio, { strategy: 'fast' })
console.log(tempo, best.loopStart, best.loopEnd)

In Node, decode a WAV with the built-in decodeWav and call the same functions — the analysis API is (Float32Array, sampleRate) everywhere.

Subpaths

| Import from | What it gives you | | --- | --- | | pleco-xa/feature | mfcc, chroma, melspectrogram, spectral centroid / bandwidth / rolloff / contrast / flatness, rms, zcr | | pleco-xa/loop | loop detection — one entry point, four strategies, one honest confidence | | pleco-xa/convert | hz ↔ midi ↔ note, time ↔ frames ↔ samples, hz ↔ mel, amplitude ↔ dB | | pleco-xa/segment | recurrence matrix, agglomerative & Laplacian segmentation | | pleco-xa/sequence | DTW, Viterbi, RQA, event/interval matching | | pleco-xa/decompose | HPSS, nn_filter, softmask, fingerprint vocal separation | | pleco-xa/effects | time-stretch, pitch-shift, remix, trim, split | | pleco-xa/filters | mel & chroma filter banks | | pleco-xa/bpm | tempo engine | | pleco-xa/notation | note / key / interval / svara notation | | pleco-xa/recurrence · pleco-xa/linalg · pleco-xa/cluster · pleco-xa/intervals · pleco-xa/playback · pleco-xa/audioio · pleco-xa/file · pleco-xa/fileio · pleco-xa/io | recurrence, eigensolvers, k-means, interval theory, playback controllers, codecs, streaming readers, WAV I/O |

Highlights

• Zero dependencies, pure ESM — runs in browsers, Node, and Web Workers.
• ~89 kB min+gzip for the entire engine — the feature subpath alone under 8 kB. No WASM, no model download.
• TypeScript declarations for the barrel and all 19 subpaths.
• 47 CI-gated test suites (420 tests) — loop points locked against committed golden fixtures on real audio (±10 ms).
• Loop detection — the signature feature.
• Real-time streaming analyzers and a live tempo tier.
• Pure-DSP vocal separation — no model, no weights, no GPU.

For AI agents

A machine-readable capability map ships with this package: llms.txt (package root) — the full function index, per-task routing, contracts, and verified recipes in one skim. The complete guides also ship inside the npm package under docs/. Also served at plecoxa.com/llms.txt.

Documentation

Full guides, a per-function API reference, and an interactive gallery where every one of 50 demos runs live in your browser: plecoxa.com.

License

MIT — created and maintained by Cameron Brooks. See NOTICE for third-party algorithm attributions.