That would be an interesting spotify hack. Start recording 2 minute tracks. Would be a similar situation to 50s and 60s radio.
About your point with indie artists vs top 40- it seems to me to be a problem with fragmentation. Top 40 has much more overlap between listeners and casual music fans vs a much more curated play list for the indie music lover. So out of 100 casual music/top 40 fans the playlist is more or less the same. However two indie rock fans have a higher probability of having fewer tracks overlap in their playlist.
About your point with indie artists vs top 40- it seems to me to be a problem with fragmentation. Top 40 has much more overlap between listeners and casual music fans vs a much more curated play list for the indie music lover. So out of 100 casual music/top 40 fans the playlist is more or less the same. However two indie rock fans have a higher probability of having fewer tracks overlap in their playlist.