If these chips are in different machines, won't they be a tiny bit detuned from each other? No two crystalls are 100% in tune.
But nevertheless, slight detune is a well known way to richen the sound. It was for example a widely used technique to enhance the sound of the antique big-box disk music boxes. Another 80's computer I have actually place the speaker right in front of the cooling-fan which creates a bit of detune effect as well.