One of the most important functions of a conductor is to cue musicians to begin playing, particularly if they have waited silently for a long time; if the cue is not clear, they might not start playing in the right place. I found that our subjects would frequently withdraw gestural information suddenly before giving a cue. That is, their EMG signals (particularly from the left bicep) often went to nearly zero before signaling the onset of an important event or entrance. Such an event happened in P1’s session at bar number 32 of the Dance movement in Prokofiev’s Romeo and Juliet Suite; many of the woodwinds need to play after many measures of silence. Leading up to this event, P1 used his left hand normally, and then, two measures before the wind entrance, stopped using it completely. Then, just in time for the cue, he gave a big pickup and downbeat with the left arm. In repetitions of the same passage, the same action is repeated. This is demonstrated in Figure 18, from P1’s left biceps signal:
In a second example, P1 demonstrated this flatlining feature in his left bicep at the beginning of an extreme crescendo in the string section. During this passage, corresponding to measures 3-7 after A in the last movement of Tchaikovsky’s Symphony no. 6, P1’s right biceps continued to beat regularly.
In an example from subject P3 I found two successive flatlines, flanking a gradual decrescendo. These events were interspersed by four repetitions of a theme. These repetitions alternate in emphasis, switching twice from medium loudness (mezzo forte, mf) to extra loudness (fortissimo, ff). The segment begins with the second theme of Sousa’s Washington Post March, followed by an answer in a complementary theme (conducted softly in the right bicep while flatlining in the left) followed by a second statement of it (conducted forte in both arms). This is followed by a bridge (conducted piano with less motion in both arms), leading to a repetition of this whole section. Leading up to the fourth repetition, perhaps for emphasis, there is a longer flatline section and a much higher-amplitude EMG signal.
The extreme effects in the EMG signals in this section might be attributed to the fact that this data was taken during a concert and this segment is from the first piece on the program, so there may have been a desire to start off with a rousing piece. P3 starts the piece with very big, accented gestures, and then lets the tension decrease way down; at the recap of one of the opening themes, he flatlines before it in order to offset it and thereby amplify the contrast.
A reasonable hypothesis for why these "flatline" phenomena occur could be that the sudden lack of information is eye-catching for the musicians, and requires minimal effort from the conductor. The quick change between information-carrying and non-information-carrying states could be an efficient way of providing an extra cue ahead of time for the musicians. It is also possible that the flatlining phenomena in these examples from conductors are reflective of similar phenomena in other areas outside of human musical behavior. For example, snakes coil before striking, cats pause before pouncing, and windspeeds and barometric pressure decrease right before the arrival of storms. There is a known neurological principle called ‘preparatory inhibition’ which also describes similar phenomena in human behavior.