Consider two pieces of music: a string quartet, Beethoven Op. 135, and his Sextet Op. 71.
The string quartet, of course, is for two violins, a viola, and a cello. These instruments are quite homogeneous and have a similar sound texture. A phrase could pass from one to another and only a very keen ear would notice it.
On the other hand, the sextet is for two clarinets, two bassoons, and two horns. These instruments are quite heterogeneous and have very different sound textures. Most people could tell them apart even if they could not name the instruments.
Another example would be pieces for a string orchestra and a standard orchestra.
Is there a term to indicate these two relationships?