Re: When is an artist considered "Mainstream"?
Who really cares what is mainstream or not? You listen to what you connect with. Music used to define class, lyrics were mostly confined to folk songs sung in bars by the drunk, where the upper class went to the symphony, and lyrics were confined to opera. Now it much less defines class as it does personal taste. Todays Billies are just as likely to listen to rap as they are jazz. Most jazz had no lyrics, most blues did, and in all genres of music you had songs with and without lyrics, except maybe rap [none that I know of]. Electronic music for clubs, no lyrics, they're not needed. Music does not need lyrics to be successful, but it needs lyrics to get on top 40 radio.
There has always been plenty of music that was mainstream but had no lyrics, Kenny G was all over the air, Yanni [did I just say that?!] the list is long, just not as long as those that add words to connect to a listener where the words matter as much as how the notes are arranged.