  In this paper, we present an EEG study of two music improvisation
experiments. Professional musicians with high level of improvisation skills
were asked to perform music either according to notes (composed music) or in
improvisation. Each piece of music was performed in two different modes: strict
mode and "let-go" mode. Synchronized EEG data was measured from both musicians
and listeners. We used one of the most reliable causality measures: conditional
mutual information from mixed embedding (MIME), to analyze directed
correlations between different EEG channels, which was combined with network
theory to construct both intra-brain and cross-brain neural networks.
Differences were identified in intra-brain neural networks between composed
music and improvisation and between strict mode and "let-go" mode. Particular
brain regions such as frontal, parietal and temporal regions were found to play
a key role in differentiating the brain activities between different playing
conditions. By comparing the level of degree centralities in intra-brain neural
networks, we found musicians responding differently to listeners when playing
music in different conditions.
