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 StoreiOS 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.
Learn more →Tonic FX
On the App StoreiOS 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.
Learn more →NewTonic EP
On the App StoreiOS 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.
Learn more →NewTonic AP
On the App StoreiOS 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.
Learn more →NewKR Editor
On the App StoreKronos 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.
Learn more →Rsf2
In storesSoundFont .sf2 editor
Merge, split and reorder presets — byte-exact and on-device.
Learn more →RDX
On the App StoreFM synth .syx bank editor
Open, preview and build .syx banks from classic FM synths.
Learn more →REXS
On the App Store.exs to SoundFont converter
Organize, play and convert your .exs instruments to SoundFont — without Logic.
Learn more →NL4 Editor
Coming soonNord 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.
Learn more →NX Editor
Coming soonNuma 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.
Learn more →In the press
A news post on Tonic 2 — a three-layer synth for iPhone, iPad and Mac: 3D wavetables, a Vector XY pad, a 12-mode arpeggiator and eight sound models per layer, standalone and AU/AUv3.
Read the article →A feature on Tonic — an analog-modeling synth with eight synthesis engines, three layers, analog filters and AUv3.
Read the article →Focused tools, no distractions
Audio apps to create, organize and play your music — no ads, no tracking. Crafted with care, in Brazil.