Multi Track Player
A professional stem player that puts the full band in a musician's hands — giving performers and rehearsal directors precise, independent control over every instrument in a track, anywhere, on any device. Now being rebuilt as Simply Playback, a multi-tenant platform serving multiple companies from one deployment.
Overview
The challenge was simple to describe and complex to solve: musicians needed a way to rehearse with a full backing track while being able to isolate, mute, or solo any individual instrument stem — in real time, in the rehearsal room or at home, without specialist hardware.
The result is a purpose-built stem player delivered entirely in the browser. Audio stems are stored securely on Wasabi S3 and streamed on demand, with per-song authorised access tokens generated server-side via PocketBase. Each stem’s volume is controlled independently through the Web Audio API, giving performers the feel of a mixing desk in a lightweight interface that works on any device — laptop, tablet, or phone.
The content management side is a custom-built admin panel integrated directly into the app. Administrators can create and organise song libraries, group them into themed collections (each with its own album artwork), manage user accounts, and distribute local-mode data exports — all without touching a database or writing a single line of code. The entire platform is invite-only: new musicians receive a branded onboarding email with a one-click account setup link, then land directly in the player.
Particular care was taken with the offline and local modes: for studio or touring environments without reliable internet, the app can run entirely from a local data export, loading stems from the file system via the File System Access API. This meant designing a single codebase that adapts its data layer at runtime — the same UI code powers both the cloud-connected and fully offline experience.
The project is live at multitrack.sonicartistes.com and is actively used by the Sonic Artistes musician community.
Build log
1 entry
What this thing is for
Short tool for layering audition backing tracks with a click track. Built it for myself first — musicians submitting to Carnival cruise auditions need a reliable way to play along without buying Ableton. Nothing fancy, two tracks, tempo, a metronome. Goal: under 200 lines, no backend.