It appears to be not generally known, but there are two types of Bluetooth. This causes great confusion.
The original one is now known as Bluetooth Classic, or BR/EDR. This is the one you would use to listen to music from your phone on headphones.
The latest one is called BLE, or Bluetooth Low Energy. This is often used with battery powered equipment, as the name suggests.
The problem is that whilst these have underlying similarities, and are controlled by the same administrative body, they are totally incompatible.
Some units support one, some the other, and some (usually phones and Linux systems), both.
Since the H9 was designed before BLE was introduced, it only supports Bluetooth Classic.
Bt MIDI is more recent, and requires BLE (it was originated by Apple to use BLE), hence the H9 does not currently support it.
So, the DIN approach would be your best way.
