Some early NRBQ ("Flat Foot Floozy" is a great chicken pickin' song), some Dwight and Pete, some Marty Party, and lots and lots of Byrds.
Most people's concept of the Byrds stops when David Crosby leaves. For me, that's about when it begins. My collection starts with Sweetheart of the Rodeo and goes on to Farther Along. I grew up listening to the canonical harmonies-and-Rickenbacker sound of classic Byrds. I know "Eight Miles High" and "Mr. Tambourine Man" and "Turn Turn Turn", and frankly, I've been done with them for a good long time now. They sound like the early 1960s. Sweetheart sounds like the mid-60s. In a good way, of course. I like the album. But it has old production. It sounds old. Dr Byrds and Mr Hyde sounds old. It often sounds like you let a hot country picker in on a Nuggets garage band recording. I mean that in the good ways — Wouldn't it have rocked to have Brent Mason or Pete Anderson on "Touch Me, I'm Sick"? — but I mean it in every bad way, too.
There's lots not to like about Untitled and Byrdmaniax and Farther Along. But they sound modern. They sound contemporary. They have tracks that could still, today, be released on radio. "B.B. Class Road" has the annoying 70's "songs about touring" bit, but by music alone, it's close to early 90s Travis Tritt and Marty Stuart. "Tiffany Queen" sounds close to Wilco's first album, AM, back when they still could twang.
I'd have to look at it deeper, but I think it comes down to production. 1970 is about the time when 24-track boards became more common, and that lead to a certain openness in production. Listen to Forrest Gump and you'll see. It uses period music, and through his college years, into his war years and to his shrimping time, you hear music that was recorded, if in stereo, on four-to-eight tracks, and the way they did that was to record what they could, mix it onto two tracks, then use what they had left to do overdubs and the like. With a 24-track board, you could record everyone simultaneously or not and not have to make those decisions until the final mix. In context, you have Forrest. He's in buildings, he's around people, he's in the jungle or in the football stadium, in the White House or in New York with Lt. Dan, and he's constrained, and the music, originally 4-track stuff, feels constrained. Then he decides to run, and they show him running through the deserts and open spaces of the west. And they play "Running On Empty" by Jackson Browne, which, in the soundtrack, was the first big-board recording. Wide open spaces, wide open sound.
Much of the later Byrds stuff sounds wide open like that.
And it also contains some of Jackson's first song sales, like "Jamaica Say You Will".