This episode made me laugh so much XD
Ritsu is tired of being at the back, after seeing video recordings of their past performances, in which the spotlight is never on her. She then goes around trying new instruments, except for Mio's bass, which she claims it's Mio's sacred place and will never touch the bass position.
In the 2nd half, Yui comes up with a lot of ideas, albeit weird and funny ones, to make Ritsu shine in the spotlight. Yui's idea of "communicating" with Ritsu aaaaaaaaaaaand Ritsu gets freaked out.
Yui is then walking home with Azusa and Yui exclaims that she'll play the drums behind Azusa if Ritsu quits drumming.
Watch the rest yourself!