I used to wonder that as well.
Think of Guns -n- Roses recording "Knockin' on Heaven's Door". I imagined Matt doing like Axl in that song. While the drums were still playing, he'd stop and say, "Okay, I want every body in this room to clap when I do!" Then they'd play the chorus and every body would clap. Then he'd stop and say, "I can't hear you!" and they'd do it again.
However, this did not happen.
Maybe they have just enough close friends planted in the audience who model what to do and every one else just follows suit.
I have an early recording of Thursday, and no one seems to be "lalalala"-ing.
Every one used to sing "Starlight, starbright" with Roger during "Paid to Think."
When "See You Thru" debuted in Nov 99, I remember watching Parrish and Matt clap and think, "That's different." There were no fans at that show, so no one knew to do it. By the 3rd time they performed it in Mar 00, it was catching on to clap along with the song.
With "God Save...", I first heard it at its 1st or 2nd show, and somehow everybody in the audience just knew when to say "whew!"
I can't grow a beard, and I don't like to party.
~Matthew Tiberius Pelham