Studiolab

Unlike great musical productions, great songs do not depend on amazing sounds and effects. You can write one on a beach, using a guitar, pen and paper.
Studiolab is a tool for writing songs. Start with an empty composition or with a known song. Use musical patterns for filling the song with music, so you can make major changes with a few, small edits. Experiment with the structure, chord progressions, musical patterns, melodies, arrangements and lyrics until you are satisfied. You can even collaborate with friends.
You can export PDF scores, MIDI and audio. Create and share your own sounds and composition templates. Almost all Studiolab features can be used offline. The iPhone and iPad versions have the same features, but the iPad is naturally easier to use.
Studiolab is a huge, evolving project for composing music. Most features are described in the in-app documentation.