will
sound a B when C is printed.Orchestration
Orchestration is "the art of employing instruments in various combinations... [and] includes the concept of instrumentation -- the study of the properties and capabilities of individual instruments." Orchestration in the Middle Ages was largely limited to forces available, and were typically scored merely to double the vocal parts. The use of instruments for specific effects and in specific combinations mark the Baroque period, to create both contrast and doublings between orchestral forces.
As composers moved away from the counterpoint (as such) of the Baroque into a style of simpler, more straightforward voice relations, their use of instruments changed as well. The first violins "became the focus of the orchestrator's attention, with lower strings often assigned a rhythmically simpler background." Similarly, the role of the winds to merely sustain the harmony was greatly reduced in complexity and difficulty. Mozart, however, "resurrected" the use of woodwinds for melodic functions, and as he and the other Mannheim composers came to appreciate these instruments, they prescribed more melodic material for them, especially the clarinet and bassoon.
What Mozart did for the winds, Beethoven did for the brass. While he did not at all abandon the winds -- he was one of the first to use the piccolo -- Beethoven used the horns "as independent brass instruments" rather than just "to blend with and buttress the woodwinds." Opera in the Classical period had already necessitated more dramatic orchestration, prefiguring Beethoven's "advances in symphonic orchestration."
Berlioz was perhaps the most significant symphonic composer of the Romantic era. He saw the process of composing and orchestrating as interwoven, not conceived independently. He also experimented with timbre, introduced bowing techniques, harmonics, and other instrumental effects. Later, the invention of the valved horn liberated composers (and players) to use the instrument with much greater versatility. Wagner continued the trends of Romantic music with his elevation of the wind instruments in importance, though the strings were still paramount.
Debussy reacted to the Wagnerian Romantic models with "high sublte orchestration" that "[elevated] woodwinds, more often scored soloistically than sectionally, to the level of dominance," and "preferred the brass section muted and provided equally understated parts for percussion."
The 20th century gave us the neoimpressionists (Respighi, Messiaen), with the "coloristic aesthetic of Debussy;" the neoromantics (Nielsen, Prokofiev, Shostakovich), who followed the Wagner/Mahler/Strauss model; neoclassicists (later Stravinsky, Copland), who "attempted to imitate the clarity and economy of Classical orchestration;" and pointillists (Webern, Schnberg, and other serialists) who used tone rows in clever arrangements to provide "a constantly shifting array of colors. Additionally, composers like Varse, who exercised the concept of composer for the sound itself, not just the relationships of harmony, and Orff, whose works created "highly unusual ensembles," introduced new scoring concepts and sonic possibilities.
Transposing Instruments
The transposed instrument is one
whose notated pitch is different from (but related by transposition to) its
sounding pitch. This variance may be in either direction, depending on the
instrument, and may exceed an octave or require alternate clef assignments. A
transposed instrument usually attaches to its name the key to which it is
tuned, relative to C; for instance, trumpet in B will
sound a B when C is printed.
The lack of valves in early brass, especially the horn, necessitated the use of transposition to avoid having to own an instrument in all the principal keys to be played. Today its usefulness is in simplification of playing these keyed instruments, including woodwinds. And although most orchestral scores use the traditional transposition of these instruments, some contemporary works score them at actual pitch, eliminating the usual transposition.