Other notes used are the chord notes. The more accentuated a beat is, the more "basic" notes are used. This is demonstrated in most of these 2 measure variations:
The bass pattern depends of course on the music category. Here are some examples:
The preset styles in the keyboard can often give good inspiration for the bass pattern - as well as for all other instruments.
The bass pattern must match the drum pattern, especially the Bass Drum. To avoid conflicts listen carefully to only these two instruments.
Another problem arises when other accompaniment instrument are playing in the same octave as the bass. If the piano plays the root notes in the left hand, the bass must play the very same notes. The lowest guitar notes may also collide with the bass.
Generally speaking this doubling of (especially root) notes has to be avoided, especially in the lower octaves. The sound simply gets too "heavy" and "stiff".