Pleco-Xa

Pleco-Xa brings musical intelligence — BPM and beat tracking, spectral features, structural segmentation, effects, pitch tracking, and its signature loop detection — to anything that runs JavaScript. No build step, no dependencies, and it does things an offline library can’t: real-time streaming analysis and intelligent loop-point detection, running live in a browser tab.

See it

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

// Decode with Web Audio, then hand the samples to the library
const ctx = new AudioContext()
const audio = await ctx.decodeAudioData(await (await fetch('song.mp3')).arrayBuffer())
const y = audio.getChannelData(0)

// Musical timing
const { tempo, beats } = beat_track(y, audio.sampleRate)
console.log(`${tempo.toFixed(1)} BPM, ${beats.length} beats`)

// The signature feature — find the best loop point
const best = await loop.detect(audio, { strategy: 'fast' })
console.log(`loop ${best.loopStart.toFixed(2)}s → ${best.loopEnd.toFixed(2)}s`)

The analysis API is (Float32Array, sampleRate) everywhere, so the same code runs in the browser, Node, and Web Workers.

What’s inside

Zero dependencies

Pure ESM, nothing to install alongside it. Runs in browsers, Node, and Web Workers — no build step, no native modules, no GPU.

Loop detection

The signature feature: intelligent loop-point finding with one entry point, four strategies, and a single honest confidence score.

Musical timing

Tempo and beat tracking, onset detection, and tempograms — numerically validated against committed reference fixtures.

Spectral features

STFT, mel spectrograms, MFCC, chroma, and the full family of spectral descriptors (centroid, bandwidth, rolloff, contrast, flatness).

Real-time

Worker-safe streaming analyzers and a live tempo tier — analysis an offline library structurally can’t do.

Pure-DSP vocal separation

Surprisingly capable source separation with no trained model, no weights, and no GPU. It runs in a browser tab.

Built to be trusted

• Full TypeScript types on every export and subpath — autocomplete works out of the box.
• Fixture-verified across ~20 domains and checked in CI, many results numerically exact.
• Explicit tiers, never silent. Quality is the default; fast/live variants are separate named calls, and anything that can’t produce a valid result throws with diagnostics rather than fabricating a number.

Ready? Install and run your first analysis → or watch every example run live on your own audio in the gallery.