Joe "King" Oliver recorded "Wawawa" in the '20s. Bubber Miley, Cootie Williams, trumpeters, and Tricky Sam Nanton, trombonist, of the Duke Ellington Orchestra pioneered in using plunger mutes ("plumber's helper") to create wah-wah sounds.
The effect was used in the '30s on "Sugar Blues" by commercial Dixieland trumpeter Clyde McCoy, who built a long career around the sound, and even today has a popular wah-wah pedal by VOX named after him. "The Fat Man" the first hit by Fats Domino features Fats singing vocal trumpet wah-wah. Another New Orleans singer, Chuck Carbo frequently performs vocal wah-wah.
Karlheinz Stockhausen notates the use of the wah-wah mute in his Punkte (1952/1962) in terms of transitions between open to close using open and closed circles connected by a line (Erickson 1975, p.73).
A familiar use of the wah-wah sound by trumpets today is the Peanuts cartoons. In the majority of cartoons, adults didn't speak, the sound they produced was a wah-wah sound. The most well known is Charlie Brown's teacher.
Wah-wah effects can also be achieved by using a vocoder to modulate an instrument sound, and speaking "wah-wah" into the modulation control input of the vocoder. The vocoder then impresses the formants of the spoken sound into the musical sound.