Mash Lab — free online song mashup maker

Mash Lab is a free, browser-based tool for making mashups of two songs. Upload two tracks (audio or video) and it automatically detects each song's BPM and musical key, separates them into stems — vocals, drums, bass and other — and time-stretches both onto a single beat grid so they play in sync. A beat-align editor lets you nudge the timing, balance each deck's volume, match keys, and add reverb or echo. Export your mashup as an MP3 or a vertical reel video for Instagram, TikTok or YouTube Shorts. No signup, no install — it runs in your browser with AI-powered stem separation. Only mash up music you have the rights to use.