In the most resonant group, the brass, the strongest instruments are the trumpets, trombones and tuba. In loud passages the horns are only one-half as strong, 1 Trumpet = 1 Trombone = 1 Tuba = 2 Horns. Wood-wind instruments, in forte passages, are twice as weak as the horns, 1 Horn = 2 Clarinets = 2 Oboes = 2 Flutes = 2 Bassoons; but, in piano passages, all wind-instruments, wood or brass are of fairly equal balance.
It is more difficult to establish a comparison in resonance between wood-wind and strings, as everything depends on the number of the latter, but, in an orchestra of medium formation, it may be taken for granted that in piano passages, the whole of one department (all 1st Violins or all 2nd Violins etc.) is equivalent in strength to one wind instrument, (Violins I = 1 Flute etc.), and, in forte passages, to two wind instruments, (Violins I = 2 Flutes = 1 Oboe + 1 Clarinet, etc.).
It is still harder to form a comparison with instruments of little sustaining power, for too great a diversity in production and emission of sound exists. The combined force of groups of sustained resonance easily overpowers the strings played pizz. or col legno, the piano played softly, or the celesta. As regards the glockenspiel, bells, and xylophone, their emphatic tone will easily prevail over other groups in combination. The same may be said of the kettle-drums with their ringing, resounding quality, and also of other subsidiary instruments.
The influence of the timbre of one group on another is noticeable when the groups are doubled; for instance, when the wood-wind timbre is closely allied to the strings on the one hand, and to the brass on the other. Re-inforcing both, the wind thickens the strings and softens the brass. The strings do not blend so well with the brass, and when the two groups are placed side by side, each is heard too distinctly. The combination of the three different timbres in unison produces a rich, mellow and coherent tone.
All, or several wind instruments in combination will absorb one department of added strings:
| 2 Fl. | + | 2 Ob. | + | Vns I, | |
| or: | 2 Ob. | + | 2 Cl. | + | Violas, |
| or: | 2 Cl. | + | 2 Fag. | + | 'Cellos. |
One department of strings added to the wood-wind in unison produces a sweet coherent quality, the wood-wind timbre still predominating; but the addition of one wind instrument to all or part of the strings in unison, only thickens the resonance of the latter, the wood-wind timbre being lost in the process:
| Vns I | + | Vns II | + | 1 Ob., | |
| or: | Violas | + | 'Cellos | + | 1 Cl. |
| or: | 'Cellos | + | D. basses | + | 1 Fag. |
Muted strings do not combine so well with wood-wind, as the two tone qualities remain distinct and separate. Uniting plucked strings and percussion with instruments of sustained resonance results in the following: wind instruments, wood and brass, strengthen and clarify pizzicato strings, harp, kettle-drums and percussion generally, the latter lending a touch of relief to the tone of the wood-wind. Uniting plucked strings and percussion with bowed instruments does not produce such a satisfactory blend, both qualities being heard independently. The combination of plucked strings with percussion alone, is excellent; the two blend perfectly, and the consequent increase in resonance yields an admirable effect.
The relationship which exists between string harmonics and the flute or piccolo constitutes a link between the two groups in the upper range of the orchestra. Moreover, the timbre of the viola may be vaguely compared to the middle register of the bassoon and the lowest compass of the clarinet; hence, in the medium orchestral range, a point of contact is established between the quartet of strings and the wood-wind.