It's really difficult to discern what constitutes Mainstream (insert format here) music today for two reasons:
* More sub-genres of musical formats than ever. In years past, there were not as many specialized sub-formated (again, insert format here) radio stations, online or over the air.
* As others have pointed out, it is much easier to access music today, so music that would've been considered Underground/Indie years ago may not be today.
"I have just been more than a little suspect of all the trades since the Willy (Scott Williamson) cash grab. That one left such a bad taste in my mouth that even a 1985 Dom Pérignon couldn't cleanse it." -- Creek14