[Footnote 8: Of late years sometimes two tubas are employed, by Glazounov for instance in his Finnish Fantasia. (Editor's note.)]
The directions are the same as in the preceding table for wood-wind. It is evident that in all three classes the formation may vary as the composer wishes. In music for the theatre or concert room page after page may be written without the use of trumpets, trombones and tuba, or some instrument may be introduced, temporarily as an _extra_. In the above table I have given the most typical formations, and those which are the most common at the present day.
_Note I._ Besides the instruments given above, Richard Wagner used some others in _The Ring_, notably the quartet of tenor and bass tubas, and a contrabass trombone. Sometimes these additions weigh too heavily on the other groups, and at other times they render the rest of the brass ineffective. For this reason composers have doubtless refrained from employing such instruments, and Wagner himself did not include them in the score of _Parsifal_. Some present-day composers (Richard Strauss, Scriabine) write for as many as five trumpets.
_Note II._ From the middle of the 19th century onward the natural brass disappeared from the orchestra, giving place to valve instruments. In my second opera, _The May Night_ I used natural horns and trumpets, changing the keys, and writing the best notes "stopped"; this was purposely done for practise.
Though far less flexible than the wood-wind, brass instruments heighten the effect of other orchestral groups by their powerful resonance. Trumpets, trombones, and tubas are about equal in strength; cornets have not quite the same force; horns, in _forte_ passages, are about one half as strong, but _piano_, they have the same weight as other brass instruments played softly. To obtain an equal balance, therefore, the marks of expression in the horns should be one degree stronger than in the rest of the brass; if the trumpets and trombones play _pp_, the horns should be marked _p_. On the other hand, to obtain a proper balance in _forte_ passages, two horns are needed to one trumpet or one trombone.
Brass instruments are so similar in range and timbre that the discussion of register is unnecessary. As a general rule quality becomes more brilliant as the higher register is approached, and _vice versa_, with a decrease in tone. Played _pp_ the resonance is sweet; played _ff_ the tone is hard and "crackling". Brass instruments possess a remarkable capacity for swelling from _pianissimo_ to _fortissimo_, and reducing the tone inversely, the _sf_ [music symbol: decrescendo] _p_ effect being excellent.