Permutations of Harmonics #8-9-10

Exercise for male overtone singers.
Fundamental: A= 110 Hz.
The exercise is based on the principles of permutions:

8-9-10; 8-10-9;
9-8-10; 9-10-8;
10-8-9; 10-9-8.
or
Do-re-mi; do-mi-re;
re-do-mi; re-mi-do;
mi-do-re; mi-re-do.

Other material may be applied to the same principles, for example harmonics #4-5-6 (do-mi-so) or the difficulty level may raised by singing permutations of four notes:
a-b-c-d; a-b-d-c; a-c-b-d; a-c-d-b; a-d-b-c; a-d-b-c;
b-a-c-d; b-a-d-c; b-c-a-d; b-c-d-a; b-d-a-c; b-d-c-a;
c-a-b-d; c-a-d-b; c-b-a-d; c-b-d-a; c-d-a-b; c-d-b-a;
d-a-b-c; d-a-c-b; d-b-a-c; d-b-c-a; d-c-a-b; d-c-b-a.

Permutations of 3 notes gives you 6 permutations
Permutations of 4 notes gives you 24 permutations
Permutations of 5 notes gives you 120 permutations
Permutations of 6 notes gives you 720 permutations

Find your own level, pitch and pace!