  Collaboration is built on trust, and establishing trust with a creative
Artificial Intelligence is difficult when the decision process or internal
state driving its behaviour isn't exposed. When human musicians improvise
together, a number of extra-musical cues are used to augment musical
communication and expose mental or emotional states which affect musical
decisions and the effectiveness of the collaboration. We developed a
collaborative improvising AI drummer that communicates its confidence through
an emoticon-based visualisation. The AI was trained on musical performance
data, as well as real-time skin conductance, of musicians improvising with
professional drummers, exposing both musical and extra-musical cues to inform
its generative process. Uni- and bi-directional extra-musical communication
with real and false values were tested by experienced improvising musicians.
Each condition was evaluated using the FSS-2 questionnaire, as a proxy for
musical engagement. The results show a positive correlation between
extra-musical communication of machine internal state and human musical
engagement.
