It's always been about the SONG (most of all), the singer and (increasingly) the packaging. All mixed with luck.
My parents are totally into 60's music - rock, pop and folk. And it's interesting to me, because SOME of those songs were great but a lot of those singers were marginal and not infrequently, they were ugly (just saying).... But you learned the song on the RADIO (so looks and performance show didn't matter). You loved the SONG (and only later saw what Mama Cass looks like - and by then, you didn't care) A lot of the performers were pretty stiff, just singing in front of a camera (Elvis being a huge exception) But you look at groups like the Rolling Stones, and see the transition to VISUAL in addition to audio. But even thing, the physical looks of the performer didn't matter (much) - again, with exceptions (Elvis.... Pat Boone).
It seems MTV changed all that for rock and pop (less so Country). People learned the song from TV.... and the VISUAL aspects became a big part of why it sunk or swam. Including singers needing to be better looking. It was SONG, singer(s) and the visual performance (and luck). The boy bands of the 90's were perhaps about the visual as much as the audio.
Now, while TV still plays a role ("The Voice" etc.), it's mostly the internet and YouTube. It means to ME, for MOST, it's back MOSTLY to the music... the teenies and tweenies are still into cute (witness Justin Bieber), the whole Disney music thingy, but I think the elaborate videos of the past are just not around much. I actually think this is good. I think a GOOD singer from out of nowhere - who maybe isn't the best looking or greatest dancer and maybe never was on TV) has a better chance now. I think it's more about the music.
My half cent. At most
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