Audio tools for iPhone, iPad, Mac & Android — and for your family!

RSJB is an independent Brazilian studio that builds apps focused on music and family — no ads, no tracking!

Our apps

Three tools, one philosophy.

Rsf2

On the App Store

Merge, split and reorder presets — byte-exact and on-device.

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RDX

Coming soon

Open, preview and build .syx banks from classic FM synths.

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Tonic

Coming soon

Three layers, eight filters and an effects rack — standalone and AUv3.

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Focused tools, no distractions

Audio apps to create, organize and play your music — no ads, no tracking. Crafted with care, in Brazil.