Music Memos by Apple - An app to capture your song ideas
SoundGrail - SoundGrail Music App designed for pianists, guitarists, and DJs.
Cardsmith - Capture ideas and collaborate in real-time
Figure - Propellerhead creates world-class software products and services that inspire music makers and provide the foundation for a worldwide creative musical community.
Bandlab - Capture, nurture, and collaborate on song ideas in the cloud
keezy - A colorful soundboard. Play with music.