Houses that have pits that hold about 45 musicians can do much of the standard repertoire. There are reductions (many quite good) of operas by Puccini, Verdi, Gounod, and Bizet for 38 to 45 players. Some were made by the composers themselves. Puccini, for example, created a reduced La Bohème. Strauss reduced Salome (from 106 players to 78) and Elektra (from 115 to 84), and the reductions are commonly used in the US except in the largest houses like the Metropolitan Opera or the Lyric Opera of Chicago. Skilled conductors have arranged reductions for a variety of reasons, including the requirements of touring opera companies. Any of these reductions is a re-orchestration. Using such a reduction is far preferable to using the original orchestration and reducing the string corps to get down to 45 players. Such a skeleton orchestra sounds more like a band.

There are occasions when “pruning” a couple of players is required—with a full orchestra or even a reduction. If the problem is pit space, some theaters may allow a couple of instruments to play behind the pit or on the side of the pit in some works. If no one can play outside the pit or if cutting a few players is driven by budget considerations, the decision about how to prune is generally left to the conductor, who is in the best position to optimize; i.e., judge what can be cut based on how the orchestra at hand can compensate in the work at hand. Note that this is situational; there’s no cookbook formula.

Acoustics don’t drive the choice of orchestration, however. Orchestration is, after all, one pillar of composition and it’s about more than decibels. (That is, large orchestras can play a gorgeous, hushed sound while small groups can make a lot of noise.) Controlling decibels alone is a matter of judgment, technique and, of course, experience. For example, bel canto operas were written for valve trombones which are much less robust than the slide trombones used almost exclusively today. Part of my job is knowing this and making judgments about how to balance within the orchestra and between the orchestra and the stage. Beyond urging the trombones to play softly, I may tacit (silence) a player in certain passages. Of course, this is not to suggest that acoustics don’t matter. There are houses that simply present problems. School auditoriums, for example, with little or no fabric or carpet can be very “live” and favor the orchestra. Something as simple as lining the pit with carpet remnants can help.