So I think your data consists of an array of ints; the index into the array is the 'chord index' and the value is the chordValue associated with that index.
If you want to associate each chord with a letter then I'd add 'a' to the chord index to get the chord letter (so 'a' becomes 0, 'b' becomes 1 and so on). I guess that when you encounter a chord you would first check against the existing known chord, and if none matched you'd allocate the next available index and store the chord value in it.
It would be easy enough to access the chord values in EEPROM by providing read and write access functions that handled the translation between the int array your application is dealing with, and the byte array that the EEPROM interface presents.