Here the dovetailing of parts is carried throughout, yet in the third bar the third and fourth horns double the fundamental bass in octaves.
The trombone is a very familiar instrument, and little needs to be added to what has already been said about it. There are slide and valve trombones. The former is the kind always employed in symphonic orchestras. The reader will recognize the instrument by the action of the player’s arm in moving the slide in and out. This shortening and lengthening of the tube of the instrument changes its key and thus enables the player to produce in open tones every note of the chromatic scale. The valve trombone is played with keys like those of a cornet. It is less brilliant and sonorous than the slide instrument. Trombones were employed as far back as Monteverde’s “Orfeo,” early in the seventeenth century, but there seems to have been no definite use of them till the time of Gluck. He thoroughly appreciated the majestic dignity of dramatic utterance of which the trombone was capable, and he used it with eloquent effect. Furthermore, he established for all time the custom of writing for trombones in three parts. After him, as Gevaert pertinently notes, the three trombones became a distinctive feature of dramatic scores, for the classic symphony found no use for their immense sonority till Beethoven called it to his aid in voicing the triumphant emotions of the finale of the Fifth Symphony. Nevertheless, the trombone is not necessarily an instrument to be used only in producing great volumes of tone. A beautiful example of its value in rich and subdued harmony, in company with other instruments, is to be found in the accompaniment to Sarastro’s grand air in Mozart’s “Magic Flute,” as is shown on the following page.
The three trombones, as in this example, usually play three-note chords, except when required to play in unison. The tuba fills out the harmony by doubling the bass part in the lower octave, or forming a four-part chord with the three trombones. There are tubas in several keys, but it is customary to write for the instrument without making any transposition. There is a fine tuba solo, in unison with the double-basses, at the opening of Wagner’s “Eine Faust” overture, and frequent examples of harmony for three trombones and tuba are to be found in the works of the Bayreuth master. In writing for the full brass choir alone a composer has the choice of several methods. He may give the melody to a trumpet or cornet, and use the other instruments for the harmony, or he may let a horn (or two horns in unison) take the melody. If he desires much force, he may give the melody to a trumpet and double it with a trombone. The natural method, however, is to let a trumpet, which is a good soprano voice, sing the air, while the other trumpet and three of the horns take the middle voices, the fourth horn and first and second trombones the lower middle voices, the third trombone and tuba the bass. Similar methods are employed where the brass joins with the rest of the orchestra in the thunder of a tutti fortissimo. The reader will find a most admirable example of this style of writing in the climax of the prelude to “Lohengrin.”