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Playback++ is a local browser audio workspace built for single-track rehearsal, synchronized multitrack stem review, batch conversion, selective export, loop practice, and fast per-track adjustments such as pitch, speed, volume, pan, mute, solo, and ordering.

Core DSP engine: audiostretch.js with a stereo phase-locked vocoder path for live playback.
Live defaults: DSFACTOR 2, LOG2LEN 11, FRAME_LEN 2048, STEP_LEN 512, CHUNK_LEN 1024.
Ranges: pitch -12 to +12 semitones, playback rate 0.1x to 2.0x, stereo output, 8 queued audio buffers.
The bundled local server launchers use Python 3 http.server to host Playback++ on localhost.

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Welcome to Playback++. This workspace is built for quick single-track practice, synchronized multitrack review, batch conversion, waveform scrubbing, loop rehearsal, selective export, and fast track-level adjustments without leaving the browser.

Helpful shortcuts:
Space = Play / Pause
S = Stop
A = Set loop start
B = Set loop end
L = Reset loop
Shift + Move Up / Move Down = send a multitrack stem directly to the top or bottom

If multitrack playback gets heavy on your system, consider using the built-in visual controls such as lower refresh rate, reduced spectrum rendering, No Audio Spectrums mode, and compact tracks.

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The stretching and pitch-shift algorithm used by Playback++ was originally designed around processing one track at a time. In multitrack mode, using pitch and speed changes on several tracks simultaneously can overload lower-spec systems. If resource usage becomes high, consider using the built-in visual controls such as lower refresh rate, reduced spectrum rendering, No Audio Spectrums mode, and compact tracks.

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Closest to source matches the nearest supported output type. Playback++ only encodes MP3 and WAV, so MP3, OGG, M4A, and AAC sources export as MP3, while WAV, FLAC, ALAC, and AIFF sources export as WAV.

Bitrate, PCM depth, and sample rate are still resolved per exported item, as closely as the available source metadata allows.