Halley Labs is an independent music label and audio software workshop based in Hamilton, Ontario, run by the producer and digital artist known as em (also credited as msx). The project's gear-side output comes from its plugin imprint, originally branded HL SØUNDSØFT and later as Comet's Tail Toybox, which releases free VST instruments and effects for desktop production.

The Halley Labs plugin catalog leans toward experimental and lo-fi sound design rather than emulations of classic hardware. Releases include SOTA (Sound of the Ancients), a single-oscillator synth inspired by the work of Sota Fujimori, and GREAT WALL, a synth aimed at harsh-noise and texture work. The label also distributes sample packs, stems, chiptune source files, and instrument templates for trackers and DAWs.

The operation is intentionally small and self-published: distribution is handled through the label's own Bandcamp and the broader msx.horse hub rather than mainstream storefronts, and the project has stated it does not maintain accounts on streaming services or most social platforms.

Halley Labs has 1 product cataloged on Equipboard, including Synth Plugins.