Not sure who needs to hear this...

If you cup your hand over your balloon knot and open and and close it rhythmically ( 🤌🏻🫴🏻🤌🏻🫴🏻🤌🏻🫴🏻) while you let 'er rip, you get a wah-wah-wah-wah-wah-wah-wah-wah sound.