Harmonics are useful for support and embouchure. Practicing this duet in this way will greatly improve your sound. You can use vowels to make the harmonics smoother and easier.
Flute Colors arrangements
Sheet music with extended techniques for flute
Here you can buy and download sheet music of arrangements with extended techniques for flute.
Variations on well know flute exercises, traditional songs, but also modern pop songs. From Drouet and Bach to Justin Bieber and Bruno Mars. Have fun with extended techniques for flute!