Here are some things I tried that I found to be VERY effectively when playing with a guitarist who loves to hammer out power chords...
- If the guitarist is playing nothing but power chords, then that opens up a huge opportunity for you. Assuming you know enough theory to figure out the key signature you're playing in, simply playing an appropriate 3rd (major, minor) once in a while will go a LONG way.
- I agree that it's sometimes hard to do anything but follow the guitar if it's playing fast power chord changes. But maybe if the guitar hits a point where it plays an ascending line, you could pick some points where you DESCEND going from one note to the next. Now all of a sudden you're playing in a different octave, with an even greater separation between you an the guitar,
- Obviously, the opposite is also true. If the guitar is playing a line that is basically descending, you can play the same note but ascending. Again, you're suddenly playing in a different octave than you were, and may now be in the same register as the guitar, giving you the opportunity to play some lines as unisons.
- If the guitar is playing lightning fast, slow down what you're doing - maybe playing quarter notes or half notes
- If the guitar is playing slowly, play a faster bass line.
- If the guitar is hammering out a rhythmic pattern with the same power chord for a longer time ( a measure or two, or even more), you can do a simple ascending or descending walk up to or down to the root of the next chord.
That's just a start, but hopefully you get the idea - a guitarist who basically plays power chords leaves a LOT of room for you to do some very simple things that can make the song a lot more interesting than just loud, distorted power chords. YOU have an opportunity to add some melodic content the wall of mud your guitarist is blasting out. Look at it as an opportunity and run with it!
