What defines progressive music?

I can suggest some old stuff from the seventies. These were the first "prog" albums I got into when I was a kid:

Moving Waves- Focus

Octopus- Gentle Giant

200 years After The Last War- Omega

Lark's Tongues In Aspic- King Crimson

Birds- Trace

Space Ritual- Hawkwind

The Inner Mounting Flame- The Mahavishnu Orchestra

UFO- Guru Guru

There. My beginner's Guide to "Prog- rock.

As for your first two questions I think that Peter Rideout is more qualified to respond in that area!

Definition of the prog-genre : a genre which has a rock( or metal) base but extends its boundaries to classical music and/or jazz.

• Recommended metal-prog albums :

          -Watchtower : "Control and resistance" (1989)

          -Queensryche : "Rage for order" (1986)

          -Ark : "Ark" (1999)

          -Ice Age : "the great divide" (1999)

          -Fates Warning : "Perfect symmetry" (1989)

          -John Arch : "A twist of fate" (2003)

          -Enchant : "Wounded" (1996)

• Recommended metal-fusion albums :

          -Spastic Ink : "Ink complete" (1997) [feat. Ron Jarzombek of Watchtower]

           -Jordan Rudess : "Feeding the wheel" [2001, current DT keyboardist,

                                       with Steve Morse, Terry Bozzio...]

          -Liquid Tension Experiment : "LTE 1" (1998) [members of DT]

          -Derek Sherinian : "Planet X" (1999) [former DT keyboardist, with

                                         drummer extraordinaire Virgil Donati]

• Recommended pomp-prog albums :

          -Rush : "Power windows" (1985)

          -Saga : "Heads or tales" (1983)

• Recommended symphonic prog-rock albums :

          -Genesis : "A trick of the tail" (1976)

          -Yes : "Close to the edge" (1972)

           -Camel : "Moonmadness" (1976, or for a more up-to-date sound : "Dust

                         and dreams", 1991)

          -Emerson, Lake & Palmer : "Tarkus" (1972, very symphonic) or "Brain

                                                     salad surgery" (1973,more experimental)

          -UK : "UK" (1978)

          -Transatlantic : "Bridge across forever" (2001)

• Recommended hard-prog albums :

          -Van Der Graaf Generator : "Pawn hearts" (1971)

          -King Crimson : "Red" (1974)

• Recommended folk-prog albums :

           -Jethro Tull : "Thick as a brick" (1972)

          -Renaissance : "Sheherazade and other stories" (1975)

• Recommended continental prog albums :

           -Le Orme : "Felona e Serona" (1973)

          -Reale accademia di musica : "Reale accademia di musica" (1972)

          -Locanda delle fate : "forse le lucciole non si amano piu" (1977)

           -Los Jaivas : "Alturas de Macchu Picchu" (1981)

          -Sagrado Coraçao da terra : "Farol da liberdade" (1991)

• Recommended neo-prog albums :

          -Marillion : "Misplaced childhood" (1985)

          -IQ : "The seventh house" (2000)

• Recommended canterbury albums :

          -Caravan : "In the land of grey and pink" (1971)

          -Happy The Man : "Crafty hands" (1978)

          -National health : "Missing pieces" (1994, tracks from 1974-1975 sessions)

• Recommended electronic/New Age albums :

          -Synergy : "Electronic realizations for rock orchestra" (1975)

           -Patrick Forgas : "Synchronicité" (2002)

          -Robert Fripp : "A blessing of tears" (1994)

          -Jon Anderson : "Olias of sunhillow" (1976)

          -Tangerine dream : "Tangram" (1980)

          -Mike Oldfield : "Ommadawn" (1975)

• Recommended space-rock albums :

          -Gong : "Angel's egg (1973)

          -Pink Floyd : "Dark side of the moon" (1973)

• Recommended fusion-jazz albums :

          -Bruford : "One of a kind" (1979)

          -Brand X : "Moroccan roll" (1977)

          -Dixie Dregs : "Unsung heroes" (1981)

          -Kenso : "Yume no oka" (1991)

• Recommended Zeuhl albums :

           -Magma : "Mekanikh destruktiw kommandoh" (1973)

          -Magma : "Köhntarkösz" (1974)

• Recommended art-pop albums :

           -Kevin Gilbert : "Thud" (1994)

          -Kate Bush : "Hounds of love" (1985)

          -Tori Amos : "Under the pink" (1994)

• Recommended new wave of american prog albums :

          -Echolyn : "Suffocating the bloom" (1992)

           -IZZ : "I move" (2002)

I won't recommend albums for other sub-genres (ambient, RIO, krautrock, art-rock) as I don't know them enough to do so.

At first, prog music to me is smth complex, strange and unusual. It shuold involve polystilistic and innovative tendencies. But i don't like modern prog and prefer good old 69s 70s bands. Sometimes it's hard to categorize their music but usually it has lots of prog elements.

My advices

Yes - Fragile. Peter Hammill - The chameleon... Jethro Tull - Aqualung. Catapilla - S/t. There are so much good progressive in 70s

Thank you all for your answers. I am aware of JT since i got to High School :)

Having listened to Dream Theater , Pain Of Salvation , Jethro Tull , Pink Floyd , Genesis, Fates warning Rush, Queensryche and some other "classic" progressive groups, i would like to get deeper and come in touch with other progressive groups that are not well-known but they have good music (ie. Van der Graaf Generator and Procol Harum ) :)