Best progressive rock album side

I’m not sure how "progressive rock" is defined.

1). If it includes "psychedelic folk-rock", I suggest "On the Shore" by Trees.

2).  I’m pleased to see "In the land of Grey and Pink" by Caravan appear on the list. I haven’t thought of that album since the underground radio station days of the late 1960s (where I was delighted to listen to it in the studios of Phoenix’s KDKB/KCAC under auspicious circumstances many times).

3).  If "progressive rock" extends to early Mothers, I’d add "We’re Only in it for the Money" or "Uncle Meat".

4).  Maybe the term can be stretched to cover "It’s a Beautiful Day" side 2.

5). Finally, I would be absolutely remiss to overlook "Balaclava" by Pearls Before Swine". It may be the pinnacle of progressive rock as I understand the term.

Anyway, very interesting discussion and thanks for starting it!

@kacomess - somebody else who knows 'Pearls Before Swine'! I don't think I'd call them prog as much as Tom Rapp seemed more like the more surrealistic Dylan stuff. Their first album, 'One Nation Underground', is also excellent... 

I'm a big fan of Caravan and the whole Canterbury scene as well... Actually got to see them in Berkeley in the late 70's....

Zappa's early stuff on Verve is by far my favorite of his... 

I know it's a digression, but since you mentioned Zappa/Verve, the unnerving prescience of "Trouble Coming Every Day" on "Freak Out" keeps coming to mind. I saw the original Mothers line-up play at the Phoenix Star Theater shortly after "Freak Out" was released. A memorable show (almost on par with Capt. Beefheart at the "Fox West Coast Theater" (an abandoned cinema taken over as a concert venue) in Long Beach, CA circa 1972 where The Magic Band performed with "It's a Beautiful Day"

Enough with the naysayers. The more music one listens to, the more one realizes there is great music in all genres from all periods of time. You have to be curious and seek it out with an open mind. Only close-mindedness would generalize quality of musicians based on genre. Absurd to say such things. That said, when recording quality comes into play some music is unfortunately simply unlistenable on a revealing system. It’s like people saying this tweak or that component must be overpriced and not be worth the money (or provide great sound quality) when they haven’t even hooked it up to their own system and listened. At the end of the day this hobby and the love of music or a passion. If you don’t have the passion and a desire to enjoy the journey find another hobby!

Frank Zappa 

Hot Rats whole album