Main Screen

On the top left you can select sounds (for Soundfont Engine) or presets (for Synth Engine).

Second selector from the left toggles between Normal mode (music note icon), Arpeggiator (up/down arrows icon) or Strummer (hand icon).

Third selector from the left enables to toggle between Synth (waveform icon) or Soundfont player (play icon). Dial button opens current engine controls.

Fourth selector from the left toggles between Free Mode (keyboard icon), Key Mode (key icon) or Replay Mode (repeat icon).

You can set sound volume with this slider or tap info icon to open About screen.

Here chord buttons live – just hold and press them and pick piano note to set chord root. Use pencil icon to configure this section further.

Here you can setup maximum number of inversions, Special Modes and chord voicing. Bass Mode adds octaves below while playing the chords (long press to turn off), Octaver works for single notes and adds 1 octave up or down (long press to turn off). Hold mode allows to layer melody notes on top of held chord. Press pencil to enable/disable elements of this section.

Keyboard view. In its top bar, you can (from the left): show less octaves, show more octaves, set octave down and up

Red button can help you in any situation that app behaves weird. It will reset all MIDI notes and sound engine. If it sill doesn't help – restart the app.