Bitwig's own tutorial channel opens this Grid walkthrough by reframing what an instrument actually is. In The Grid, instruments don't have to respond to notes at all - a sine wave routed directly to the audio bus produces a continuous drone that can be shaped and controlled over time without any MIDI input.
From there, the focus shifts to building a note-free drum sequencer using the Gates module. Dropping Gates onto the trigger input connects it instantly, and it starts playing immediately - which raises the question of where the clock signal is coming from.
The answer is Device Phase, a setting built into the Poly Grid device itself. It feeds a phase signal as a pre-cord before anything else is connected, so any sequencer you drop in is automatically synced and running. Out of the box it runs at 16 sixteenth notes, which maps to one bar of 4/4 time, and you can halve that to 8 sixteenth notes to run the sequencer at twice the speed.