All life has rhythm. Our physical bodies illustrate this: with the pulse of the heart-beat; with our natural reaction to night and day; and with the monthly, yearly, and seven-yearly rhythm to which we are subject. If we realize the implications of these facts, we can help ourselves considerably in matters of health and happiness by cooperating with these rhythms, or we can harm ourselves physically, mentally and spiritually, by cutting right across these natural laws.
Music is an expression of life, and there is comparatively little of it which does not call for an appreciation of rhythm - even though it be in a very subtle way.
In training a band - especially if it be young or immature - the conductor should seek to make the players understand something about rhythm, at any rate its elementary form. They should know where the 'strong, medium, weak' accents appear within the bar; and they should understand also that the conductor's basic baton movement indicate these varying accents, as well as indicating the tempo of the music.
Once this is thoroughly appreciated it will help the bandmaster considerably in his work. Sight reading will improve, for a player with a strong sense of rhythm, finding himself in difficulties in one bar, will know when to jump to the next, and so keep up with the rest! Development of this rhythmic sense will also prevent many of those wrong entries one hears so often of immature bands.
Even in slow, sustained music, the rhythm must be felt by the players; it is possible by this means to make even a single sustained chord 'live'...
Rhythm is an important factor in interpretation. More (or less) accentuation of the basic rhythm will color the music considerably; and then, of course, the accentuation of the subtle 'inner' rhythms of various small groups of notes carries such possibilities still further.
Studying such matters is a most fascinating part of the conductor's art.