ABCDEFG corresponds to the simplified musical notation 6712345, and its sound is driven by a signal of a certain frequency. The corresponding relationship is as follows (12M crystal oscillator, 51 microcontroller)

FREQ:

DB 0F2H,03DH ;Bass 1

DB 0F3H,0BDH ;Bass 2

DB 0F5H,014H ;Bass 3

DB 0F5H,0B1H ;Bass 4

DB 0F6H,0D0H ;Bass 5

DB 0F7H,0D1H ;Bass 6

DB 0F8H,0B5H ;Bass 7

DB 0F9H, 01EH ;Alto 1

DB 0F9H,0DEH ;Alto 2

DB 0FAH,08AH ;Alto 3

DB 0FAH,0D8H ;Alto 4

DB 0FBH,068H ;Alto 5

DB 0FBH,0E8H ;Alto 6

DB 0FCH,05AH ;Alto 7

DB 0FCH,0EFH ;Treble 2

DB 0FDH,045H ;Treble 3

DB 0FDH,06CH ;Treble 4

DB 0FDH,0B4H; Treble 5

DB 0FDH,0F4H; Treble 6

DB 0FEH,029H; Treble 7