I feel that in '78 it was a bit of a retro style song. Modern rock in that era sounded much different. The sax and piano hearkened back to the 50s and even 60s. He wrote a song that sounded like it was from the era he missed is how I always interpreted it.

Rock Me Amadeus is a song about how classical music was the modern rock of its day. It’s now a classic.

Same with “Jingle Bell Rock” and the lyrics about getting sentential about old Christmas songs.