People usually associate the brass instruments with noise. But as a matter of fact, wonderfully rich and soft tone effects can be produced on the brass by a composer who knows how to score for it. Just as the pianissimo of many violins is a finer pianissimo than that of a solo violin, so a much more exquisitely soft effect can be produced on a large brass group than on a few brass instruments or a single one. When modern composers increase the number of instruments in the brass group, it is not for the sake of noise, but for richer effects.
The trumpet is the soprano of the brass family. The fanfare in "Fidelio" when at the critical moment aid approaches; the Siegfried Motive and the Sword Motive, in the "Ring of the Nibelung," need only be cited to prove the effectiveness of the instrument in its proper place; and Richard Strauss instances the demoniacal and fateful effect of the deep trumpet tones in the introduction to the first act of Bizet's "Carmen."
Although the notes of the trombone are produced by a slide, this instrument belongs to the trumpet family. For this reason, in the "Ring of the Nibelung," Wagner, in addition to the usual three tenor trombones, reintroduced the almost obsolete bass trombone. He wanted a trombone group complete in itself, and thus to be able to utilize the peculiar tone color of the instrument; as witness in the Walhalla Motive, where it is scored for the three tenor trombones and bass trombone, resulting in a wonderfully rich and velvety quality of tone. Excepting Wagner and Richard Strauss, there probably is not a composer who would not have used the bass tuba here instead of taking the trouble to revive the bass trombone. But Wagner wanted an unusually rich tone which should be solemn without a trace of sombreness, and his keen instrumental color sense informed him that he could secure it with the bass trombone, which, as it belongs to the trumpet family, has a touch of trumpet brilliancy, whereas the tone of the bass tuba is darker.
Mozart employed the trombone with fine effect in _Sarastro's_ solo in the "Magic Flute"; Schubert showed his genius for instrumentation by the manner in which he used them in the introduction to his C major symphony, as well as in the first movement of that symphony, in which a theme is given out by three trombones in unison; and another familiar example of good scoring for trombones is in the introduction to the third act of "Lohengrin." In the Death Prophecy scene in the second act of "Die Walküre," a trumpet melody is supported by the four trombones, another instance of Wagner's sense of homogeneity in sound, since trumpets and trombones belong to the same family. In fact, throughout the "Ring," as Strauss points out, Wagner wrote for his trombones in four parts, adding the bass trombone in order to differentiate wholly between it and the tuba, which latter he used with the horns, with which it is properly grouped.