I'm surprised I have not posted here before since Crimson is my favorite prog band of all time.
Wonderfully eclectic band and some of their lps should be in any serious rock collction....I would recommend the first of course as well as Larks Tongues and... Red...which many prog fans consider their finest hour. 'Big Ears' above rated it lower but imho he's dead wrong and most prog heads will say so.
For me they had the most accomplished players throughout their career because Fripp wanted virtuosos.
Genesis (Gabriel era), Yes, and Gentle Giant also had some top notch players as well as a few others.
As most know 'In The Court' ....is considered by most to be the start of full blown prog rock though a few bands were doing proggy things several yrs before that album came out. Fripp said he was influenced by Sgt Pepper's use of various recording techniques as well as various sounds and blending of styles.
Not sure if I can pick a favorite lp ....I really like 4 of them quite a lot but the first made a huge impact on me so Ill post a mellow song from that classic one.
'I Talk To The Wind'- KIng Crimson..........McDonalds flute/clarinet and Giles drumming are both exquiste.