I don't think anyone just tunes into 'prog' straight away , well I didn't. I used to listen to radio a lot as a teenager and only go to serious album listening much later.

I'll try and go chronologically for mine

could have been any Beatles song but the trumpet is a big deal

psychedelic music rules!

that fantastic descending bass line!

Probably the first prog track I ever heard

A very common gateway prog song

And another very common gateway prog song

and again

then I saw ELP on the TV and was ready!

Hard to say ... but it was in Brazil that my musicla tastes were shaped, and we even got Beatles and Rolling Stones albums. But Brazil has always had a very lively and special music ability and talent, and I became aware of many popular folks, although only the names of Roberto Carlos and Maria Betania are still very vivid in mymind.

My dad's classical music collection started (sort of) in Brazil, and early enough I became aware of a lot of classical music. At 15 we came to America, and the first thing I heard was Blonde on Blonde immediately followed by The Paul Butterfield Blues Band, Mike Bloomfield and others though I still listened to rock music and eventually heard things like The Nice, Fairport Convention and was also listening to Kinks and a few other English bands.

I specially liked The Nice and then later ELP, because they brought classical music to the foreground and were, basically, playing a new interpretation, which made a lot of sense for my ears, despite die hard folks thinking that the kids did not know what they were doing and were horrible playing the classical music.

By '68/'69 and beyong, I had graduated to the hipper stuff that was around, and stuck with it for a very long time, and then later in Santa Barbara the FM radio took its roots to the limit before the stations were all sold out to various conglomerates around/before the 80's.

If I was to point to a show, or something here or other, it would be SPACE PIRATE RADIO, that right from the start in January 1874 was ahead of its time, and presented more music and experimental stuff than you have ever considered or experience within a radio station or broadcast. Even today, no one can touch Guy's feel for music and presentation. It's not a "radio show" ... it's an EXPERIENCE. 

Music, for me, has always been about the Experience, not anything else, and sometimes there is this or that, or someone calls it this or that ... but it doesn't matter ... it's the experience that counts and the rest is not important, and I certainly do not care (or like) the numbers that try to convince the readership that something it better than the rest. SPR was never about who was best or worst. And you don't know how to experience music if you have not stuck through a couple of these shows.

The rest? Fancy words and cheap talk!

           Blood, Sweat and Tears hit "Spinning Wheel" was the first record I bought and loved in the fall of 1971, and it focused my attention on getting more radio hits on 45 rpm records.

               Then I heard Steppenwolf's hit "Magic Carpet Ride" and that solidified in me a taste for heavy rock.

    My mother bought me my first album, which was Steppenwolf's "Monster" and I loved it, and wanted more lps but was not allowed to get very many until I got older.

            Mom was not a music listener, bless her, but my Dad had a collection of 1940s jazz records by artists like Woody Herman and Artie Shaw and Benny Goodman, so though I found jazz a little challenging at such a young age, it had it's effect on me.

              Another song that helped shape my taste was Alice Cooper's School's Out, and here was a rocker I knew my parents would not approve of, but that is why I bought more records by that band, and they were my favorite for quite awhile.

              Now fast forward to the 1980s, and I was kind of burnt out on heavy rock and looking for something new and was in my early 20s and though not a specific song, but a movie -Amadeus-cemented in me a long standing love of "Classical Music", and especially Symphonies, with the 1st Symphony of Mahler, 9th Symphony of Bruckner and also falling in love with the Beethoven piano sonatas opened up a whole world to me, and I started to collect classical records in 1985.

               As for progressive rock, I had been superficially aware of it, but not much, and then a friend lent me a copy of Triumvirat's Ilusions On A Double Dimple in 1985 and I was awestruck! This  was what I had been missing all these years, and was so impressed that a band from way over in Germany could kindle such an experience that changed my life, and opened the floodgates for a permanent love of progressive music.

          

King Crimson - Indiscipline, 21st Century...

Frank Zappa - Inca Roads, Didja Get Any Onya?

Gentle Giant - Design, Knots

Henry Cow - Nirvana For Mice, Industry

Peter Brotzmann - Machine Gun, Music For Han Bennink

Sun Ra - Space Is The Place, Yucatan

Penderecki - Threnody To The Victims...

And various pieces by Reich, Merzbow, Stravinsky, Ligeti, Coltrane, and things that we played when I was in middle school/high school band. 

I got into prog at the age of 12 or so, there wasn't that much before, but surely there were The Beatles, Tomorrow Never Knows and some stuff in the Yellow Submarine film - Only a Northern Song, It's All Too Much for example. I also loved Abba and felt attracted to some more sophisticated stuff of them such as Eagle.

Then came Manfred Mann's Earthband's Watch album and some Pink Floyd. Echoes made a huge impression on  me but it wasn't the first I had heard and liked of them.

Manfred Mann's Earthband were also important to me. Blinded By The Light was played a lot on the radio and I loved that soaring synth sound especially.

Abba , I remember Waterloo when that first came out and could easily have added that to my list.

Yep good ole Alice Cooper. The end of that record is actually very 'prog' in certain respects (drumming mainly). He fronts a radio show over here and actually plays a lot of prog and seems very knowledgeable about it.

I was never exposed much to classic music that much as a child or young adult. I remember liking the Mars - The Bringer of War which was used quite a lot to promote sci-fi shows but that was about it.

"Silent Night" gave me my first exposure to the raw beauty and power of music--to the transformative effect that music could have--even when performed live, by one's own self.

The voice of radio music show host Karl Haas provided me with the awareness that a lot of work and thought (and other stuff) went into creating the music we hear on the radio.

Motown soul let me know the depths of emotion (and mischief) that could be expressed through music.

Marvin Gaye's album What's Going On? let me know that music could express pain and frustration in beautiful ways.

"Inna gadda da vida", "Closer to Home (I'm Your Captain)", "Stairway to Heaven", "Papa Was a Rolling Stone", and "American Pie" let me know that rock and roll didn't have to fit "hit radio" time limits.

"Nights in White Satin" always sucked me into a dreamy Lewis Carroll type of rabbit hole and the spit me out limp and ragged.

More than any song ever, "Bennie and the Jets" affected me so deeply, so singularly, so unexpectedly, and in so many ways that it is, without any doubt or hesitation, the single most powerful "first time" hearing event of my life. The indescipherable singing. The syncopated piano play. The "is it live--in front of an audience--or not?" feeling. The odd yet addictive chorus. The dramatic key shifts. The amazingly engaging and unusual outflow. The David Hentschel synthesizer. and so much more. To this day, I always turn it up and listen to it to its finish whenever I hear it.

For me, I guess, it's more albums or album sides than just particular songs. Those that were in my parents collection that appealed to me: Sounds of Silence by Simon and Garfunkel (for the melodies and the vocal harmonies), Tchaikovsky's Symphonie pathétique (for the symphonic qualities) and the sound-track of Jesus Christ Superstar (for the narrative quality and the distorted guitars, but not in a punk way... Somewhere in '77 or '78 we went to see the theatrical performance in London, which was very impressive for a kid of 9, 10 years old!). Then, some things that were on the radio, notably Pink Floyd's The Wall (I was 11, 12, by then), I discovered Alice Cooper's Halo of Flies that was very very intriguing. A year or so after that, my elder brother bought Kayak's Merlin album and I was especially mesmerized by the A side of that album, for how it combined those melodic, symphonic, rock and narrative qualities...

Then, through some of my friends I discovered a bit of Rush, Saga, Focus, Ekseption, Rainbow, before, at 15, entering a record shop to buy my first vinyl: I was hesitating between a Judas Priest album or Yes' 90125. I bought the latter and the rest is history...

Before I got into prog (which happened when I first heard 'Meddle' back in 1972), I'd say these are some of the key songs that influenced me.

How Much Is That Doggie in the Window? - Pattie Page (the first song I ever remember hearing on the radio)

My Boy Lollipop - Millie Small (the first song ever to truly excite me).

Zabadak - Dave Dee Dozy Beaky, Mick & Titch (just so hypnotic)

Eleanor Rigby - the Beatles (one of many Beatle songs that are outstanding for me)

A Whiter Shade of Pale - Procol Harum (beautiful Baroque rock/pop)

Nights in White Satin - The Moody Blues

Son of a Preacher Man - Dusty Springfield (still my favourite non-prog female singer of all time)

Amazing Grace - Judy Collins (possibly the most beautiful a capella recording ever)

In the Summertime - Mungo Jerry

I Hear You Knocking - Dave Edmunds (this marked the point when something clicked and I realised that rock & roll was quite wonderful)

My Sweet Lord - George Harrison

The Banner Man - Blue Mink (just a truly great happy sing-along anthem)

Get It On - T.Rex

Brown Sugar - The Rolling Stones

Won't Get Fooled Again - The Who (just epic)

...which takes us through to the end of 1971, then round at the house of one of my school friends in early '72 I heard Meddle, and that was a total game changer for me, and still getting excited listening to prog almost 50 years on.

It's perhaps easy to forget just how clever Elton and Bernie were as song writers back in the day.

Probably the one that impacted me most was Philadelphia Freedom. It just has that almost indefinable quality that takes me away. Love the strings!

I love that song to death although can't remember it it impacted me so much when I was young.

Also leads me to another great song of the late sixties Where Do You Go To My Lovely? by the British folkie Peter Sarstedt. Ones to listen to on a bleak rainy Sunday afternoon in a dark quiet room..

lots of interesting selections , but would like to pick up on Dave Edmunds. Quite an amazing guitarist , Sabre Dance (Love Sculpture) is an oft overlooked major event of prog rock imo

 Perhaps one of the greatest 'guilty pleasures' of the seventies 

I should probably add that at pretty much the same time prog came to me in the shape of Manfred Mann's Earthband and Pink Floyd, I also got into post punk. The Cure's Play for Today and Comsat Angels' Independence Day where super-influential songs. And also at that time I heard and was impressed by Wuthering Heights.

I didn't know what to make of Kate Bush in 1978 so mostly just ignored her lol!