Drop Tuning refers to the re-naming of notes when changing the tuning to a lower pitch one half step or more down on guitar or bass.
To aid musicians not familiar with note names outside the standard EADG(BE) or whatever the original tuning is, choosing -1, -2 etc. will cause the instrument to be lowered in pitch by one, two half steps etc. without the original note names being changed.
Any Sweetener settings chosen in conjunction with a drop tuning setting are preserved and applied to the correct strings.
Capo Tuning refers to raising the pitch by means of a Capo d'Astro. To aid musicians not familiar with note names outside the standard EADG(BE) or whatever the original tuning is, choosing +1, +2 etc. will cause the instrument to be lowered in pitch by one, two half steps etc. when the capo is applied to the first, second fret etc. without the original note names being changed.
The alternate Key setting are used for instruments played in a key other than the key of C. The note display will change so the proper note for those instruments will be shown. Common examples would be Saxophone (Eb), Trumpet (Bb) and French Horn (F) | 
