For quick checks and recording (or in case you do not have a
MIDI device at hand), you can also use Hydrogen's
Virtual Keyboard. It emulates note triggering via
MIDI NOTE_ON events (see MIDI Note Rendering) but currently only supports order-based mapping in Input Mode
Key strokes in the Virtual Keyboard do also not trigger Actions associated with NOTE_ON events.
The figure below depicts which keyboard key is associated with which
instrument number in Input Mode
Drumkit or instrument
pitch in Input Mode
When using German or French keyboard layout the overall mapping is still the same.