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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, one philosophy.

Tonic Synth

On the App Store

iOS synthesizer

A synthesizer for iOS and Mac: three layers, eight sound engines per layer, ten analog filters and a full effects rack — standalone or inside your DAW.

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Tonic FX

On the App Store

iOS effects rack

An effects rack for iOS and Mac: 37 effects you build, reorder and play live — drive, modulation, voice, delay, reverb, EQ and dynamics.

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New

Tonic EP

On the App Store

iOS electric piano

An electric piano for iOS and Mac built from physics, not samples: tine, reed and E.Grand, stereo from birth, with a 16-effect rack.

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New

Tonic AP

On the App Store

iOS acoustic piano

An acoustic piano for iOS and Mac built from physics, not recordings: a grand and an upright you build part by part, eight microphones and a room.

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New

KR Editor

On the App Store

Kronos editor

Turn a knob on the iPad and your keyboard changes right away. Scenes that don't cut, a Set List you sort with a finger, and your backups in order.

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Rsf2

In stores

SoundFont .sf2 editor

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

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RDX

On the App Store

FM synth .syx bank editor

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

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REXS

On the App Store

.exs to SoundFont converter

Organize, play and convert your .exs instruments to SoundFont — without Logic.

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NL4 Editor

Coming soon

Nord Lead 4 editor

A panel with all 86 parameters, reading the keyboard's banks, organizing and writing them with verification, sound conversion and a stage setlist.

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NX Editor

Coming soon

Numa X Piano editor

All four Zones of your keyboard on one screen — sounds, effects, levels and six colour scenes that switch without a cut, live.

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In the press

Focused tools, no distractions

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