Changes in instrument combination patterns in Western classical orchestral music are traced over a three hundred year period from 1701 to 2000. Using a stratified sample of sonorities from 180 orchestral works by 147 composers, various empirical analyses are reported. These include analyses of instrumentation presence, instrument usage, ensemble size, common instrument combinations, instrument clusterings, and their changes over time. In addition, the study reports associations of different instruments with various dynamic levels, different tempos, pitch class doublings, affinities between instruments and chord factors, as well as interactions between pitch, dynamics, and tempo. Results affirm many common intuitions and historical observations regarding orchestration, but also reveal a number of previously unrecognized patterns of instrument use.