The would have been songs of the early rock era. I was a big oldies station listener when I was 12-14 (1987-1989), and the music at that time spanned from about 1955 (“Rock Around the Clock”–heck, I dedicated the song “Only You” by the Platters on the oldies station to my 8th grade sweetheart in 1988) to about 1969 or so (I remember “Age of Aquarius/Let the Sunshine In” being about the most recent music they would play. After that, you’d have to switch to the “classic rock” station, although “classic rock” overlapped a little bit of the oldies station, starting in the 60s and going through the 70s. The oldies station would play more the pop hits of the 60s, while the rock station would play, well, the rock hits.)
I’m 40, of that lost not Millenial not X generation. 80s and 70s stuff does sound old timey to me, even though I grew up in the 80s. 70s rock was the stuff of war movies.
Ah, a Xennial! That said, I was born in '75 and my wife is '77 and my brother is '81 and they all feel like Xers to me.
Anecdote:
A few years ago, I was having dinner at Culver’s, and there was a group of teenagers (probably about 14 or 15 years old) in the restaurant. Among that group was a young couple, arm in arm – he was wearing a Led Zeppelin t-shirt, and she was wearing a Bob Marley t-shirt.
The first thing I thought was, “that’s cool, they’re into old-school music!” And, then, I thought about it a little more.
They were wearing shirts for artists who had peaked 35 years or so earlier…and, yet, those artists were still relevant to these teens. When I was 15, it was 1980, and had I, at that time, been wearing a t-shirt for an artist from 35 years prior, it would have been a Benny Goodman or Les Paul t-shirt, which would have been pretty much unheard of among kids in my generation.
I suspect that there’s a definite pre-post divide for music; whether that’s currently in the 1950s (i.e., pre-rock-and-roll), the 1960s, or the 1970s, is an interesting question.
Or the T-shirts are being worn ironically, or because they’re retro-cool - not necessarily because the wearer digs their music.
Entirely possible. 
In any case, it wouldn’t have even occurred to 15-year-old me to have worn a shirt from a 1940s musician, for any reason.
I’ll add that, last month, my wife and I went to see Electric Light Orchestra in concert, and we were accompanied by my niece (age 26) and her husband (age 30), both of whom love ELO. (My niece’s other favorite artist is Stevie Nicks.)
My 19 year old daughter loves The Beatles, and has seen McCartney twice in concert. She also loves The Doors, The Who, Led Zeppelin, and Bob Dylan.
My 15 year old son loves Jethro Tull. A couple weeks ago I took him to a Jethro Tull concert in Huber Heights, OH, and he loved it. He also loves Zappa/MoI, Black Sabbath, and The Velvet Underground. He wears a Zeppelin shirt everywhere he goes.
Born in 82, Rock and Roll from the 50s and doowop sounds old timey to me. 60s and on not so much. Even stuff I dig like Elvis has an unmistakable old timey sound. But I grew up with the Beatles all around. I grew up with Bowie and Led Zeplin and The Doors and Stones and the Who played everywhere all the time. “classic rock” was HUGE in the mid to late 90s when I was in middle and High School. That’s the reason why the garage rock of the mid 2000s became a thing. Kids my age who grew up on late 60s rock wanted to make rock that sounded like that. So you get the Strokes and the White Stripes.
Kids in their 20s now grew up, it seems, with the 80s being similarly fashionable so synthesizer sounds are back. It’s a cyclical until someone actually breaks the mold and makes something really brand new.
I have a 16yo daughter (so not a “millennial”) and to her it’s all just “music”. Yeah, she understands that some songs are “old” but her approach to music and her sense of identity with it is far more about “here’s what I like which is a reflection of who I am” and not “here’s what I like as a means of setting myself in opposition to anybody else”.
For example, on her playlist are Celtic songs, Frank Sinatra, Ariana Grande, Mozart, One Direction (and Harry Styles, always Harry Styles), Tom Rosenthal, Harry Connick Jr, her Rockabilly phase, her “moody girl” phase, Led Zeppelin, movie soundtracks ranging from Disney Tunes to Guardian of the Galaxy 70s compilations to the Avengers soundtracks, Rhianna, Alanis Morissette, The Beatles, The Who, Benny Goodman & Glenn Miller, etc etc etc.
The kid knows more music… and knows more about music… than I ever had the chance growing up in the late 70s/early 80s, and it’s all because of YouTube. Yeah, Pandora/Spotify helped, but YouTube is the primary driver of musical tastes for her generation as it is ubiquitous, free, easily accessed, easily shared, and did I mention free? You can find, for almost any song ever, the original, the original with lyrics, the original set for karaoke, covers, instructional “how to play” videos, etc.
She and her friends spent years sharing new songs with each other, learning the lyrics, more… and they all did it via YouTube.
And it leads to surprises like that time I was listening to the oldies station with her and 2 friends in the back seat (about 12yo at the time), when Chicago’s “Hard to Say I’m Sorry” came on… and all three of them got really excited and started belting out the song as it was playing. The song was released in 1982, this happened in 2013, so it would have been the equivalent of 1979 me singing along to a 1948 hit my Dad had on the radio. Never would’ve happened. But with my kid and her friends? Totally normal.
So I am positive that Sophia knows if a song is “old”, but I am also positive it doesn’t really matter to her.
I spoke to some of my relatives that are millenials and post-millenials; for most part they said they enjoyed listening to a lot of the music from the 70s and 80s. I bolded listening because quite a few of them said watching music videos of songs from the 70s and 80s really dated them more than the music itself.
Even if the music sounds old-timey to millenials, the 70’s are still a huge influence for all sorts of music, especially hip-hop and electronic/dance.
Yeah, I definitely get the sense that post-Gen X, into the Millennial generation, and now beyond, music became more “democratic” and less cliquish than it was when I was growing up in the 80s and in high school in the very early 90s. Certainly, IME, by the late 90s, early 00s, the answer to “what kind of music do you listen to” became less X and Y genres and more “I listen to all kinds of music” (and first with the caveat “except country and rap” to now even without that caveat.)
A lot of the “indie rock” that has been out in the past 5 or so years, to me, is like the 80s synth pop but without the synths. The rhythm, and the heavy emphasis on same, immediately makes me think of Duran Duran. That’s why bands that sound like this (and not all bands labelled as “indie rock” do so) I classify as “pop rock” instead since they remind me of 80s pop. Although I understand that “pop rock” could mean the complete opposite as well to some people, such as bands like Imagine Dragons that use pop techniques and instruments but with more of a rock rhythm.
Born in '80
Early Beatles (think: I Wanna Hold Your Hand) sounds old timey.
Later Beatles and other 60’s bands like the Rolling Stones, The Doors, Bob Dylan, Led Zeppelin, Black Sabbath are all modern. So for the most part I’d say the 60’s and forward sounds modern to my ear, and before that it’s old timey. Even 80’s synth sounds are modern sounding to me (and seem to be coming back en vogue in certain circles)
Exceptions/Special:
Motown - sounds both old timey and timeless/modern at the same time. To me, Motown is like the great uniter, in that you take any cross-section of people from various race/gender/economic status/whatever… and everyone can groove to it.
Disco- its like… it’s own thing, man.
There’s a big new trend on YouTube of millennials reacting to music from the 60s/70s/80s. It’s suddenly become a very popular thing.
I’ve not seen these but I’ve seen ones where older people listen to current music. The older people actually liked much of it because much of it was sampling from music they already knew and liked, and I’m guessing the millennials have a similar reaction, but the other way.
Mainstream pop too. My daughter is crazy about Taylor Swift so I’m extremely familiar with her most recent album, and it could be a Madonna or Debbie Gibson record. It’s not exactly 1:1 but it’s pretty darn close. Also all of the trap stuff that is hot with kids right now is all deeply influenced by the synthesizer music of the 80s. Migos, Khalid, Lil Pump, etc. Kanye West has been riding that train for years.
Not necessarily new wave sounds, but the sounds of Michael Jackson and Madonna.
Right! See post #4.
When I was 12 I was part of the “Death to Disco!/Rock 'n Roll will never die!” crowd.
Wrong on both parts!
I once called Lady Gaga “evolutionary Madonna”, which I still hold to be true.