Drumstick MIDI Monitor is a MIDI monitor for Linux using ALSA sequencer

Drumstick MIDI Monitor logs MIDI events coming from MIDI external ports or applications via the ALSA sequencer, and from SMF (Standard MIDI files) or WRK (Cakewalk/Sonar) files.
It is especially useful if you want to debug MIDI software or your MIDI setup.
It features a nice graphical user interface, customizable event filters and sequencer parameters, support for MIDI and ALSA messages, and saving the recorded event list to a SMF or text file.