The obvious one is "L" as you start with A then add 3 letters = D, then add 1 letter = E, then add 3 letters = H, then add 1 letter = I, then add 3 letters = L.
I is the next letter.
E dEsEr....E
g.
E
e
the letter E
L
P
it is ABC
e
G comes next in the musical note sequence. After G, the sequence starts again at A.
The alphabet has 26 letters. The letter "E" comes after the letter "D".The English alphabet, in order:ABCDEFGHIJKLMNOPQRSTUVWXYZ