You have all you need, Kristen?
Yep, I'm good thanks!
Oh, well, I'll post this anyway.
My obvious may not be your obvious, but I can't imagine a list without Dylan, James Brown, Hendrix, Coltrane, the Velvet Underground (as unobvious as possible at the time but hard to miss in retrospect) and Motown (although who you want to pick to represent Motown is a big topic in and of itself.) Sly Stone should be obvious but probably isn't. And to answer David's question before he asks it, yes, I'd pick Sly over Larry Graham. Without LG Sly's genius still would have found a way to manifest itself; w/o Sly LG would have been a virtuoso missing a context in which to flourish. There's also the Beach Boys, girl groups, Miles, Ornette and Southern soul. But you wanted slightly less obvious so I'll throw out a few.
1) Carole King: Brian Wilson & his hero crazy Phil are certainly important figures, but let's go with the woman who started the sixties as half of the most successful songwriting team going and started the seventies with the all-time biggest-selling album until Rumours or Saturday Night Fever dethroned it. "Will You Love Me Tomorrow" is the defining hit of the girl group era. "The Locomotion" has gone to number 1 a few times. She wrote hits for the Everlys, the Drifters, the Monkees, Aretha. Goffin-King demos were known for being nearly finished productions, not bare bones sketches; IIRC, the only thing that was changed on "The Locomtion" was swapping Little Eva's voice for Carole's. The huge success of Tapestry paved the way for the whole singer-songwriter era of the seventies. Did she invent the style? No. Were labels falling all over themselves to find similar artists after she sold eight million copies? You betcha!
2) Charles Mingus: Mingus was extremely influential in many ways, but I'm putting him here as the "pivotal figure on the pivotal instrument," as critic Martin Williams wrote. One of the key developments of the sixties is the movement of the bass out front in arrangements and recordings, particularly in pop. The process was well under way in jazz by the sixties, and when Detroit jazzman James Jamerson switched from acoustic to electric as part of the Motown house band and brought the lessons he had learned into the top 40 the tipping point had been reached. There may not be a straight line from Jimmy Blanton to Mingus to Jamerson to "Papa's Got a Brand New Bag" to Larry Graham to Bootsie to George Clinton, or from Jamerson to McCartney to Rick Danko to country rock, or from Mingus to Scott LaFaro and Charlie Haden to Ron Carter and Richard Davis, but the changing roles of the rhythm section in a group and of the bass and drums within the rhythm section are related and an important development in 20th century music. There's a research project for ya!
3) Gram Parsons: Again, there may not be a straight line from Sweetheart of the Rodeo to the Flying Burrito Bros. to the Eagles... but it isn't a very crooked line either. And whether you love Gram and hate the Eagles isn't the point. Influence is and GP really came up with the template for the L.A. sound of the seventies, and the Eagles ran with it and became zillionaires. The Eagles Greatest Hits is either the biggest selling album ever or second only to Thriller depending on whose statistics you believe.
4) the Bakersfield sound: I can't pick between Merle Haggard and Buck Owens. They were both great and both huge stars who dominated the country charts throughout the sixties and early seventies.
5) Sam Cooke: Giant influence on Otis, Aretha, Al Green, and almost every other major (and minor) soul singer. Made it seem so easy that Steve Perry thought he could sing like that. Most of the melisma on American Idol can be traced directly or indirectly back to Sam, but I won't hold him responsible for that regrettable legacy. Cooke was also important as a businessman, setting up his own label (SAR Records, i.e., Sam and Alex Records) (continued...)