Yamaha Disklaviers are compatible with Playground Sessions.
To connect your Disklavier unit to your device for use with Playground, follow the keyboard connection steps outlined here.
If your Disklavier is not being recognized by the app, follow the troubleshooting steps outlined in these two articles:
If those troubleshoots do not work for you, please check the user manual to understand the flow of MIDI signals from the unit. In most instances, you will need to adjust a specific setting or a switch to enable MIDI out signals to be sent from the unit. If you are having difficulties understanding your Disklavier, please contact Yamaha's support team for assistance.