For quickly notating songs and chord fingerings, Chord! for iOS achieves the best balance of ease, versatility, and customization of any app we’ve tried. You can select standard chords or build a library of custom chords to choose from, place those chords anywhere on the page, and import or enter lyrics if needed. When you’re done, quickly export a perfectly formatted PDF file. It’s the perfect composition notebook! If you need any help along the way it also has many learning tools and chord lookup functions. You can learn more about it at http://getchord.com/.