In actual performance, the choosing of the right tempo of a piece depends upon the artist’s understanding and apprehension of the music - its form, texture, and mood; but there are, of course, technical matters which he will have first of all to take into consideration.
The amateur band conductor must of necessity consider the standard of technique achieved by his men. However much he would like a certain allegro movement to flash and sparkle, it is useless to set a speed beyond the ability of his bandsmen. He must cut his coat according to his cloth, and try to achieve something of the spirit of the music by rhythmic accentuation and clarity of playing within the limits of the band’s technical standard.
The same applies to very slow music. It takes a very fine band to sustain an adagio movement with fine tone, just balance, and quiet intensity - retaining the interest and ‘flow’ of the music. Young and immature bands may well need to play a little above the indicated tempo in such instances.
Even in directing a top-grade group of players, the wise conductor will give every consideration to the technical demands of the music. As an example, consider a group of mast-moving, lounged semiquavers. If this is to be single-tounged, there is a speed-limit above which it cannot be well played. If the same passage is to be double-tounged, there is a speed-limit below which it cannot go. The conductor will lose no prestige if he ascertains from his players the best pace for such a passage, and as far as possible adapts his ‘reading’ of the music to the technical possibilities. It might well be that a mere two or three ‘awkward’ bars of such music will more or less dictate the pace of a whole movement.
An interesting case in point is found in the orchestral repertoire in the scherzo from the incidental music to ‘A Midsummer-night’s Dream’ by Mendelssohn. Towards the end there is a long solo passage, in fast semiquavers, for the 1st flute. These the player double-lounges, and his tempo there more or less dictates the speed of the whole scherzo. Earlier there are also quick semiquaver groups for clarinets and oboes, which are not comfortable at the flautist’s speed: but, because of the importance of his solo passage, the comfort of the other players must for once be considered of secondary importance.
There are many such problems arising in brass band music, and only the very immature or conceited conductor is likely to insist that he must always dictate the tempo.