
Using Raspberry Pi as a USB MIDI host is very simple.
Connect your MIDI USB instrument or keyboard to Pi and tie them together using a “aconnect” command (ALSA sequencer connection manager).
Example, if I want to play Korg NTS-1 with Arturia Minilab MK2.
“aconnect -l” command will give below result.
pi@raspberrypi:~ $ aconnect -l client 0: 'System' [type=kernel] 0 'Timer ' 1 'Announce ' client 14: 'Midi Through' [type=kernel] 0 'Midi Through Port-0' client 24: 'Arturia Minilab mkII' [type=kernel,card=2] 0 'Arturia MiniLab mkII MIDI 1' client 28: 'NTS-1 digital kit' [type=kernel,card=1] 0 'NTS-1 Digital Kit MIDI 1'
“aconnect 24 28” command will connect them together (aconnect sender receiver) and I can play NTS-1 via Minilab keyboard.
Type “aconnect -l” again to verify connection.
pi@raspberrypi:~ $ aconnect -l client 0: 'System' [type=kernel] 0 'Timer ' 1 'Announce ' client 14: 'Midi Through' [type=kernel] 0 'Midi Through Port-0' client 20: 'CH345' [type=kernel,card=1] 0 'CH345 MIDI 1 ' client 24: 'Arturia MiniLab mkII' [type=kernel,card=2] 0 'Arturia MiniLab mkII MIDI 1' Connecting To: 28:0 client 28: 'NTS-1 digital kit' [type=kernel,card=3] 0 'NTS-1 digital kit MIDI 1' Connected From: 24:0
Pi 3 B+ have 4 USB port and if you need more gear to connect then easily expend using USB hub.

If fancy add a small oled screen to display connection status.

I prefer manual way to do but if you want to automatic connection between gear check-out this article.
When I don’t use as a MIDI host it’s playing internet radio 24hr using Modipy.
Hi. Thanks for the information, im trying to connect I am trying to connect my BOSS katana Mk2 with my MIDI pedalboard. Do you think it is possible to do it?