CyberGene
PabloPeterson on pianos with class-compliant USB audio interface such as the Numa (and Yamaha) you have to use the so called “printer cable” which has USB-B on one end and USB-A on the other:
Then I use the Lightning to USB 3 adapter which adapts the USB-A end of the above cable to Lightning for my iPhone:
https://www.apple.com/shop/product/MK0W2AM/A/lightning-to-usb-3-camera-adapter
Once connected, I open the Camera app and make a video. The audio will not be from the microphone but from the digital interface instead.
Note that with the latest iPhones and iPads with USB-C connectors, you don’t need the adapter. You can only use a single USB-B to USB-C cable. I purchased this one that I use with my iPad Mini 6:
https://www.thomann.de/intl/pro_snake_usb_typ_c_b_cable_2m.htm
How (and if) that works on Android devices I don’t know, someone else should confirm.

