Meludia - Listening exercises and to sharpen your ear and music theory skills
Violin by Trala - Violin by Trala is a music learning app that is designed specifically for Violin users.
GNU Solfege - GNU Solfege is free music education software.
Metronaut - An app to help you play classical music
Perfect Ear - A simple yet advanced application for improving your solfege skills.
Flat - Online collaborative music score and tab editor, accessible from any device