Guitarix - Guitarix is a simple Linux Rock Guitar Amplifier for https://alternativeto.
Meludia - Listening exercises and to sharpen your ear and music theory skills
Ampire - State Space Modeled guitar amp/cab/stompbox simulator.
GNU Solfege - GNU Solfege is free music education software.
TH-U - World class guitar amps and effects for PC and Mac
Auricula - Practice your sense of hearing and learn to identify intervals for your musical development.