Symphony Pro 5 is a complete and intuitive app for writing music notation on iPad. It allows you to compose music for just about any size ensemble, from piano, symphonies, band, lead sheets, chord charts, guitar tabs, and more. Starting Version 5, Symphony Pro now offers handwriting recognition as the only in-app purchase: Perfect with Apple Pencil, and works great with touch or capacitive stylus
Symphony pro is nice for music sketches. Having 100+ various music instruments it allows to compose music in plenty of styles. What it makes different from other apps and iOS DAWs is that you work not with piano roll but with music notation or guitar tabs.
After you create music in Symphony pro it can be exported in several different formats including MIDI. There is also app for iPhone (it is not universal and if you want to use it on iPad and iPhone you need to purchase both apps).