QPainter - repaint frequently

Hello,

I'm trying to create a sort of graphic equalizer, in a nutshell a program with 10 columns changing size according to music played in the background.
I want those columns to be divided in 10 rounded rectangles with gradient, which I already got working, but my question is, how should I do the whole repainting?
Assuming I get new values from the sound file every 0.1 seconds, would I delete and create a new QPainter 10 times per second or is there some way to modify previously drawn rectangles and toggle their visibility?
I still don't fully understand how the painting / deleting / repainting should be done.

Thanks in advance,
Jay-D