The Original Harmon WOW-WOW Mute - Harmon B Model Aluminum Trumpet Wow-Wow is a most loved effects mute. The "wah-wah" sound is made by a sliding cup in the end of the mute. Acclaimed artists have utilized and supported Harmon mutes for more than 25 years. Made altogether of aluminum, the Harmon B Model is free-blowing and does not adjust or change the pitch in any way.