Lay the bow against the hollow of your cheek and make music!
Set the tension.
A wooden tuning peg from a violin adjusts the bow's tension. Here we see the tuning peg, holding peg (optional), screw, and string.
Every mouth bow begins as a flexible wooden slat or stick. If the center of your slat can be flexed 2 inches off the straight, it's sufficiently resilient.
Photo by Rick Sell