Early forms of the talk box such as the Heil Talk Box (developed in the 1970s) used the guitar amplifier’s output to drive a speaker horn that pushed air into a tube held in the player’s mouth, which filters and thereby shapes the sound leading to a unique effect. The singer/guitarist Peter Frampton made this effect famous with hit songs such as Do You Feel Like We Do. Newer devices, such as Danelectro’s Free Speech pedal, use a microphone and vocoder-like circuit to modulate the frequency response of the guitar signal.