Regard the idea of negative space in sonic terms. Initially, one might consider it to be silence, but it is more than that, and of greater subtlety.
Consider negative space to be a matter of perceived distances and surrounding areas within which notes are clustered or scattered, for instance, or of the differences in shading between various timbres. These shifting areas of negative space are as valuable as the aural "objects of focus" themselves.
Viewed in this manner, tones and lines as objects of focus are of equal-- or greater-- importance to composition when compared to the more commonplace components of music, to wit, rhythm, beat, melody and harmony.
