Huh... A few clarifications may be needed at this point, just to avoid any misinformation
Indeed, Flea used his Q-Tron on
21st Century, just like any other RHCP song that have featured an envelop filter sound, since 1998, in the studio or during live shows.
He used the Dunlop Wah only once on a song called
How Strong, written during the Californication sessions in 1999. Though, he kept the pedal on his pedalboard for the subsequent tours in 1999 and 2000.
The Bass Balls was just used only one time in 1994 while jamming on Coffee Shop in rehearsals. But as the pedal broke down just before the band went to cut the track in the studio, Flea used a Boss FT-2 Dynamic Filter on the record, so the Bass Balls never made its way on an album, nor on his pedal-board.