POLAR - A powerful document manager for Mac, Windows, and Linux for managing web content, books, and notes and supports tagging, annotation, highlighting and keeps track of your reading progress.
Scale Heaven - Browse and play any scale/chord, chord progression.
Periodical - This application calculates the fertile days according to Knaus-Ogino.
ChordIQ - Learn notes, chords, sight reading, perfect pitch and more.
Always Reading - Queue up articles and schedule when you want to read them.
7Pad Scales and chords - Music instrument and assistant for playing scales and chords.