Music Memos by Apple - An app to capture your song ideas
Better Notes - Simple notes app that ties notes together with #hashtags
Cardsmith - Capture ideas and collaborate in real-time
flomo - The minimal memo-taking tool to empower better thinking
Bandlab - Capture, nurture, and collaborate on song ideas in the cloud
Paper - Super-clean writing space with a lot of configurability that stays out of sight when you don’t need it.