McKernan was a participant in the predecessor groups leading to the formation of the Grateful Dead, beginning with the Zodiacs and Mother McCree’s Uptown Jug Champions. Bob Weir and Bill Kreutzmann were added and the band evolved into the Warlocks. Around 1965, McKernan urged the rest of the Warlocks to switch to electric instruments. Around this time Phil Lesh joined, and they became the Grateful Dead.
McKernan played blues organ as well as harmonica and vocals. While his friends were taking LSD, marijuana and other psychedelics, McKernan preferred alcoholic beverages such as Thunderbird and Southern Comfort. He steadily added more signature tunes to the Dead’s repertoire, including some that lasted for the remainder of their live performance career such as “Turn On Your Love Light” and “In the Midnight Hour.”
In 1967 and 1968 respectively, Mickey Hart and Tom Constanten joined the Grateful Dead, causing the band to take a stylistic turn from blues-based danceable rock toward full-blown experimental psychedelia influenced by avant-garde jazz, serialism, and world music traditions. Constanten often replaced Pigpen on keyboards. In October 1968, McKernan and Weir were nearly fired from the band because of their reluctance to rehearse.
Ultimately, the task of firing them was delegated by Garcia to Rock Scully, who said that McKernan “took it hard.” The remaining members did a number of shows under the monikers Mickey and the Hartbeats and Jerry Garrceeah and His Friends, mainly playing Grateful Dead songs without lyrics. Weir asked repeatedly to be let back into the band, promising to step up his playing, and eventually the rest of the band relented. McKernan was more stubborn, missing three Dead shows; he finally vowed not to “be lazy” anymore and rejoined the band. In November 1968, Constanten was hired full-time for the band, having only worked in the studio up to that point. Road manager Jon McIntire commented that “Pigpen was relegated to the congas at that point and it was really humiliating and he was really hurt, but he couldn’t show it, couldn’t talk about it.“
McKernan achieved a new prominence throughout 1969, with versions of “Turn On Your Love Light”, now the band’s show-stopping finale, regularly taking fifteen to twenty minutes. When the Grateful Dead appeared at Woodstock, the band’s set (which was marred by technical problems and general chaos) consisted mostly of a 48-minute version of the song. Not only did he have a short love affair with Janis Joplin and a longer friendship, like Janis he’s also forever part of the 27 Club. Here are Janis and Pigpen with Turn on your Love Light: