The patented automatic wah device developed in 1972. Stevie Wonder’s endorsement brought the product to national attention.
Stevie Wonder and Mutron III
“For a convincing recorded demonstration of what Mu-tron III can do, listen to Stevie Wonder on his great hit, Higher Ground. (TamlaT326L). Mu-tron III works with most electrified instruments or with microphone. Get one for yourself soon.”