[2.0][linux] getting MIDI keyboard to work

I'm running Debian Wheezy and Gnome with Pulseaudio.

With Musescore 1.2, I was able to see musescore as an alsaseq device and to connect my USB MIDI keyboard using e.g. aconnect.

With Musescore 2.0 (Debian package by tiagovaz), the application is not listed as supporting the alsaseq interface, so I cannot use aconnect to connect the midi keyboard. And the keyboard is not listed in the preferences I/O tab. The https://www.youtube.com/watch?v=IZ1b1aF9lpg uses a Mac and Portaudio, and shows a combo box with the device to use as input. I never was able to get this on my computer with Portaudio configured in Musescore.

What I had to do to get the MIDI input (and still have both Transcribe! and Musescore produce sound):

* select Portaudio
* use the ALSA API
* use the pulse device

Then Musescore is listed as an alsa sequencer port, and can be connected to the midi keyboard.

I think this should be part of the documentation, probably in https://musescore.org/en/node/39861#i-o or https://musescore.org/en/handbook/note-input or in some platform specific notes.