Android Question Looking for midi ble examples and library

Thanks.
I will give a look to study it in deep. But I think that it would be very hard.
I wish a full library, but I should have to learn about gATT, services & characteristics. and parse strings coming from BLE device.

My problem is that I have to send notes (as chords to the midi keyboard) - that is, for writing to the device - and also get the clock message (ad beat for minute) to change chords - that is, for reading from the device. The idea was to edit chord sequences with smartphone (ad tabs chords for guitar). The idea was to edit it with b4a in order to use modern GUI to edit and save songs.

But I don't know how to develop a callback (I saw some java code about midi ble).

Please Erel, could you suggest how to start using BLE 2.

I have another question. I tried the demo source and realized that my app connects to a ble device ad random. that is 2 times it connected to my ble midi device (WIDI MASTER) and the 3rd time to a fitband of my neighbor. The 4th time to another ble device and the 5th again with my ble midi device. I realized that to connect to my midi ble device I have to disconnect it from android os. So, is there a way to select visibles ble devices?

thanks in advance
lex