Free Music Sequencer

For macOS, Linux, Windows, iOS and Android
Get Helio for Windows:
portable 32-bit portable 64-bit installer

Distraction-free

Lightweight, minimalistic UI, that helps you to get into the zone and focus on your ideas. Helio is an attempt to rethink a music sequencer to create a tool that feels right.
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Clear over clever

Visualize music in a way that doesn't seem so smoke and mirrors. The app may serve educational purposes, and aims to be the tool you need to grow as a composer.

Sketching tool

Probably it won't replace your workstation at the moment, but you can use it as a quick way to compose before going into one of full-featured DAWs.
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Incomplete

¯\_(シ)_/¯
It's still a work in progress, one‑man hobby project, which I'm building for myself and sharing with the world. Many essential features are missing, so check back in a couple of years — or, better, contribute.