When playing three or four-note chords think about bow division. The bottom two notes need less bow, since they are played at the frog where the bow is heavier. The top two notes need more bow, as they are played in the lighter part of the bow.
Maintain resonance on the top two notes by drawing the bow nearer to the bridge as you move to the A and E-strings.
Check also the level of friction once the bow has settled on the A and E-strings. Too much friction and the sound will crack, too little and the sound will be weak.
For simultaneous playing of three-note chords see Three-Note Chords.
Scores - 2 + 2 Chords - violin & viola
Chords - Three-Note Chords