Repetition and Development in Prog

Good topic.   Thematic variation & development were the lifeblood of much prog, and you can hear it frequently if you listen carefully.   I think of Yes; Close to the Edge, TfTO, etc.   Composition in general has always used development but classical and Prog did it best and made the most of it.   Neat how a simple phrase, when unpacked, altered and fleshed-out, can become a major piece of work.

In a way, pop songcraft tends away from progression which may be why it's more digestible and consequently more successful (popular).
 

My favourite example of thematic repetition and development is from Gentle Giant - Pantagruel's Nativity. The first few notes is the theme, which is developed in the vocals of the verses ("How can I laugh or cry?" and variations on that building beautifully to a great contra theme), at 1:50 the theme is played by the guitar, but in a very different way, and another part of the intro is repeated. Directly after the "heavier part" with the counterpoint vocals the theme is again played, developed, the saxes play two phrases, one is the theme (rearranged a little more jazzy) and then a variation, this is repeated while the bass plays a variation on the "heavy part". They go a bit more in the background to make room for the solo, when the guitar takes over the solo the theme is building, to the repetition of the "heavy part". Then at 5:18 the theme again reoccurs now with trumpet and the bass plays a variation on the other part of the intro, in this variation it builds very powerfully to a climax which emohasizes the chromatism used in the song, leading to the last verse, recapulating "How can I laugh or cry?", but now sung with two voices. The piece concludes with a slight variation on the contra theme.

Atavachron wrote: I think of Yes; Close to the Edge, TfTO, etc.

The Argent instrumental The Coming of Kohoutek is a good example of how a 10 minute piece based almost entirely on a single theme by Liszt (Totentanz - which in turn is based on Gregorian plainchant Dies Irae) never becomes verbatim repetitive, boring or predictable. Check out the live version from 1974's Encore:

You mentioned Near Morse. I do know litte of him outside of Transatlantic, but I do feel he (even in Transatlantic) abuses the "technique". However, I think it is wonderfully used on "The Whirlwind", my favourite Transatlantic album by far, and one of my very favourites from that decade. I think mostly because of the way they used most of their themes in the overture section and then developed them throughout the rest of the album (usually I don't like how those overture things work on other albums, but on this one I really loved it). Another great example of this for me would be Edisons Children's "The Final Breath Before November" (also a wonderful album for me).

Yeah Transatlantic does it a lot too, especially Bridge Across Forever. The "Motherless Children" melody that first appears in the beginning of Duel With the Devil is repeated throughout, and makes an especially stunning return near the end with the choir. On top of that, all the songs have a theme in common (the Motherless Children section appears again near the end of Suite Charlotte Pike, sung by Roine this time. Man I could analyze that whole album it's so great. 

Magnum Vaeltaja wrote: For modern prog examples, this seems to be one of the underlying tenets of a lot of post-rock, like Godspeed You! Black Emperor's album Lift Your Skinny Fists Like Antennas to Heaven

What a keen observation! Yes, I do find it too a really creative and enjoyable feature. It has much to do with bringing what's familiar to you in a different fashion, and that is psychologically pleasing. 

In Raconteur Troubadour by Gentle Giant the same melody (vocal melody of the verses) appears throughout the song in many incarnations (the whole mid-section is basically about playing with that melody).

In The Truth Will Set You Free by The Flower Kings the opening motif reappears throughout the song in lost of places and variations).
Some other bits reappear in other songs on the album.