Encoding Messages

Demo has a hidden message, try to decode it, the result may be cryptic. (No spoilers other than its a mystery)

Character MIDI Note
A C7 Base note
B C7 (The sound is a bit quiet/is a sine wave than on other notes)
C D7
D D7 (The sound is a bit quiet than on other notes)
E E7
F F7
G F#7
H G7
I G#7
J A7
K A#7
L B7
M C8 Octave up
N C8 (The sound is a bit quiet than on other notes)
O D8
P D#8
Q E8 One octave down (C6)
R F8
S F8 (The sound is a bit quiet than on other notes)
T G8
U G#8
V A8
W A#8
X B8
Y C9 Octave up
Z C#9
0 D9
1 D#9
2 E9
3 F9
4 F#9
5 G9
6 G#9
7 A9
8 A#9
9 B9

But anyway, a concept how you can encode messages in music.