TEMPO Slider by XTAL

TEMPO Slider adds a CDJ-style tempo control panel to music purchase sites, designed for DJs and music collectors who want to preview tracks at a target BPM before buying.

KEY FEATURES
• CDJ-style vertical TEMPO fader with ±6 / ±10 / ±16 / WIDE range
• MASTER TEMPO (pitch keep) using DAW-grade Rubber Band Library compiled to WebAssembly
• BPM display with automatic extraction on Beatport / Traxsource, or manual tap input
• Keyboard shortcuts: , / . for fine adjust (Shift = coarse), R reset, M master tempo, T tap
• Mouse wheel on fader for precise control
• Draggable panel with position memory

SUPPORTED SITES (BUILT-IN)
• Bandcamp (bandcamp.com)
• Beatport (beatport.com)
• Traxsource (traxsource.com)

ADDING YOUR OWN SITES
Click the extension icon on any other music site to add it. The extension will request permission, then enable the tempo control panel.

USE CASES
• Preview tracks at your target mixing BPM before purchasing
• Audition tracks at slower or faster tempo while keeping the original pitch
• Tap to set source BPM and see live "current BPM" feedback as you move the fader

PRIVACY
This extension does NOT collect, track, or transmit any data. All processing happens locally in your browser. Source code is open at https://github.com/XTAL-JP/tempo-slider under GPL-2.0.

Note: this extension uses declarativeNetRequest to add CORS headers and remove Content-Security-Policy headers on supported sites. This is required for the audio processing pipeline (Rubber Band WASM library) to function inside the page's audio context. No data is sent externally.