How do I connect my Kawai piano to a Mac via Bluetooth MIDI?
Pair the piano in macOS Bluetooth settings, then configure your MIDI app to use the piano as its input device.
Enable Bluetooth on both your piano and your Mac. Put the piano in Bluetooth pairing mode. On your Mac, go to System Settings (or System Preferences on older macOS) > Bluetooth, find your piano in the list, and select to pair.
Once paired, open your preferred MIDI application such as GarageBand. In the app's settings or preferences, configure the MIDI input to use your piano's Bluetooth connection. In GarageBand, create a software instrument track and begin playing.