In the wake of the Summer of Love, troubadours turned their attention inward and upward, using their ample talents to champion causes both romantic and existential. The spare, outspoken political folk that occupied singer/songwriters throughout the ’60s gave way to lush, mellifluous ballads and rowdy rave-ups in which artists examined matters of the heart and soul from multiple angles. Armed with little more than a six-string, poet/philosophers like Cat Stevens and Joni Mitchell helped listeners make sense of everyday chaos, while charismatic crooners like Billy Joel and Elton John sent worries scurrying away on a cascade of piano chords.