Keep a handy pocket reference everywhere you go with Chord/Changer, the app that helps you convert chords written in alphabets to numbers so that you can play the same song in any key easily.
Simply select the Key Chart in Chord/Changer that matches the key of of the song you are converting, and then you are ready to swap all the alphabets with their corresponding numbers.
To discover how playing music by numbers allow you to play the same song in any key, and all the apps in the app suite that go well with Chord/Changer, do visit Chord/Changer's website.
*Note: An "unintended" feature that undoubtedly some people will realize is that once you have songs written in number sheets, you can use Chord/Changer to easily swap in the alphabet chords for any key if you work with musicians that can only read alphabet chords.
The creator of Chord/Changer still maintains that there is a lot more benefit to thinking and playing music by numbers and hopes to document them in the very near future. (n_n)