He is best known as the bassist and co-lead vocalist of the band Mountain, whose song "Mississippi Queen" peaked at number 21 on the Billboard Hot 100 and became a classic rock radio staple.

Originating in the eclectic music scene in New York's Greenwich Village, he became closely attached to the British power trio Cream, writing, arranging, and producing for their second album Disraeli Gears.

Upon completing his studies and returning to New York, he was unable to find work and so became part of the Greenwich Village folk-music scene, where he made a name for himself as an arranger; he appeared on albums by Tom Paxton, Vince Martin and Fred Neil for Elektra Records.

[3] He continued producing throughout the 1970s, released a solo album (Don't Worry, Ma) and recorded with Kazuo Takeda's band Creation[3] (who had opened for a reunited Mountain during their 1973 tour of Japan).

In May 1973, the British music magazine NME reported that Pappalardi would be producing and playing bass on Queen of the Night, the debut album for Maggie Bell, former singer of Stone the Crows,[4] but this proved to be false.