4.2 Other features for future treatment

In addition to the fourteen features detailed above, I found twenty-one others that I have not yet fully expanded upon. I list these below since I think that many of them are potentially significant:

  1. A corollary to point 4.1.3 about proportional EMG correlations is that the overall amplitude of the bicep EMG also seems to correlate with the relative number of people who are being led. At the beginning of P3’s concert segment, he conducted the audience, roughly 2,300 people, in a shared song. During this section, his left biceps signal was significantly larger than usual.
  2. P3’s respiration showed regular features that were very unusual; many of his inhalation peaks would have two modes, as if every intake of air was done in two stages. These seemed odd at first, but could be explained by movements or direction changes in his arms. These double peaks also resembled the breathing patterns of joggers, for whom each step causes the lungs to compresses a bit and therefore introduces a dip in the signal.
  3. P3 breathed much more deeply and expressively during impassioned violin solos than during regular-tempo march passages.
  4. P3’s GSR signal was much more radical in the performance than it was in rehearsal.
  5. Across all the subjects I found large inhalations at the beginning of every piece; this is related to point 4.1.12 about large GSR increases at the beginning of pieces. Perhaps these big changes in the moments right before the beginning of a piece provide a cue to the intensity of the music to come. Also, this phenomenon is parallel to the sharp intakes of air that people take right before making a big pronouncement or asking a question; there is something about the moment right before taking a big step that requires a preparation, and a significant intake of air seems to do that. In P3, however, a great deal of this respiration signal could be created when he raises his left arm before every piece. Even though the EMG signal doesn’t reflect this (since the arm is relaxed), the raising of the arm causes an expansion of the ribcage and therefore causes the lungs to expand.
  6. There were extreme differences between student and professional breathing patterns. Both S1 and S2 do a strange thing with their breathing; while conducting, their breathing signals exhibit a quick rise followed by a long decay. That is, they seem to breathe by quickly filling their lungs with air and then slowly exhaling over the course of a whole phrase. The resultant signal looks like a big impulse followed by a slowly decaying exponential. These patterns correspond with phrases in the music, but seem to occur more from their leaning in and making huge gestures to start a phrase, and then not being able to sustain or follow through on it. These student respiration patterns strongly resemble the signal that P3 makes while talking. In contrast, the professionals’ breathing patterns are more symmetric with respect to the EMG beats.
  7. Between musical sections there are often extreme changes in the gestures, even if the music doesn’t change very dramatically in character. Perhaps this is a purposeful technique to offset the second section from the first one, so that a return to the first section is obvious.
  8. Beat envelope types -- faster pieces tend to have EMG beat profiles which are more vertical, which suggests that faster music itself demands beats which themselves are more exponential in their rise and fall. Slower pieces have EMG beat profiles that are more gradual in their rise and fall. A "beat" is not an event of a fixed duration but rather a tension envelope that has an upward phase and a downward phase of varying parameters. Perhaps the "character" of a piece could be defined in terms of the slope of the tension signal during beats. That is, Titanic and Sousa marches could be distinguished by conductor beat-profiles.
  9. P3’s double beats – he gives gestures that appear visually to have one mode, but the biceps EMG signal has two spikes in it which seem to be timed so as to line up with two adjacent beats (or eighth-notes). It seems as if the first of the two is the pickup, and the second is the confirmation on the beat that the musicians play on. (Or are they 2 pickups?) This may be related to the double modes in his breathing patterns.
  10. Sharpness in EMG peaks seem to be an indicator of ability level. S3 had the most defined, sharpest peaks of all the students, and she was considered by her teacher to be the best of the students. Also, P3’s EMG signals seem really clear and free of extra events. In general I found more pronounced peaks across professionals and less pronounced peaks in students.
  11. Pickups and downbeats are recognizably stronger than other beats in a bar.
  12. Separation between left and right hands seems to be correlated with experience; the professionals used their left hands more independently than did the students. This is related to point 4.1.1 and is discussed a great deal in the literature of conducting.
  13. Markedly different breathing patterns between conducting, talking, and neutral behaviors. P3 showed huge differences between conducting, talking, and neutral breathing; when reciting from a written text, he takes little breaths and sustains through the phrases as much as possible; it gives the breathing a very different profile from the characteristically sinusoidal (or sometimes rectified sinusoidal) normal breathing pattern.
  14. Inhalation seems more significant for expression than exhalation; the preparation (tension) phase seems more important than release phase.
  15. I found several examples where GSR signals demonstrate small upward trends at tempo transitions. S2 particularly demonstrated small GSR increases just before tempo transitions; it was hard to tell whether or not this was truly GSR or represented inducted noise or motion artifact from respiration and EMG signals.
  16. Within a single piece, the respiration profiles usually remain constant in some way (it might deviate for a B theme but then return).
  17. Posture (verticality of the torso) compared with the character of the music -- since people tend to lean in when they are attracted and away when they are disgusted, perhaps posture while conducting has explicit affective content.
  18. I found some evidence of a Clynes’ style pulse in biceps EMG and breathing signals. Generally, exhalation is heavy, inhalation is light.
  19. Then there is a category of external effects causing apparent signals. For example, P3 sometimes bounced on his legs, which caused effects in his biceps EMG signals. In his concert data, his bouncing right knee seemed to be helping to amplify the left arm tension. (This can be confirmed with positional data from the Polhemus system.)
  20. EMG preparation before every piece. P3 always raises his left arm right before beginning a piece; the arm seems to be extremely relaxed and without force, since the left arm EMG signals show almost no tension.
  21. EMG ending of every piece. P3 grabs the end of the last held note with his left hand. Within pieces of similar musical style, similar beat and breathing patterns are common. For example, P3 conducted four different Sousa marches that could be compared statistically.