The work of directing is tightly interwoven with the work of managing change initiatives within an orchestra. A widely researched and reported fact is that up to 80% of organisational change projects are unsuccessful. A good conductor is mindful of the rebound. If the rebound is too large, the conductor must rush to get back to the focal point. If the rebound is too small, the conductor may be forced to pause to get back in tempo, confusing the beat and the musicians. Rebounds, and thus downbeats, determine the speed of the music.
Smaller downbeats are used for faster music, larger downbeats are used for slower music. The reason for this is because in fast music you don't have time to move your hands too far, and in slow music you do. To try otherwise is a waste of energy. Sound is produced when something vibrates. The vibrating body causes the medium around it to vibrate.