Bright or rich timbres coupled with loud dynamics affect moods of vigor, turmoil, conflict, and valor. The same timbres coupled with soft dynamics affect moods of sensuality, passion and compassion. Dark or simple timbres coupled with loud dynamics are encountered only occasionally in music and affect moods of starkness and loneliness. The same timbres coupled with soft dynamics affect moods of mystery and terror. These combinations are subjective to all listeners but are well understood by theater and movie composers.
Timbral combinations provide unique possibilities for music.
Often composers assign successive segments of melody or other material to different instruments. Certain orchestral combinations of instruments sound very much like other non-orchestral instruments. Instruments of music have long been associated with the natural world. Flutes, for example, very often represent the songs of birds. Musical instruments of all traditions have evolved over many centuries and each has a colorful history of development.