The aim of this work was to assess brain responses of expert cellists during a real (INT) or imagined (IMG) interpretation of two musical styles with different learning/training cognitive roots. EEGs of 12 cellists were recorded while they interpreted (INT/IMG) previously memorized excerpts of tonal-baroque (T) and atonal-contemporary (A) music and, at rest (R). Phase synchronization functional connectivity measurements among different cortical regions were computed from the EEG data and at different frequency bands (FB). These were then thresholded using surrogate data tests. Brain network construction and graph-metric analysis was performed for each FB and condition/interpretation. Global graph-indices statistical results showed that regardless of FB: a) the node degree and density presented significant differences among-conditions T, A and R during IMG and between-interpretations with INT>IMG only for A; b) global (GE) and local (LE) normalized efficiency (vs random network), indices measuring network information exchanges, exhibited a similar small-world network structure (SW) in T, A and R during INT; however, during IMG, SW changed in T and A but due to a significant LE increase with LE(A)>LE(T)>LE(R). Statistical node topographic maps results showed significant differences for graph degree (INT>IMG) and for LE (IMG> INT) in A for certain nodes of delta and theta EEG FB networks. Styles differences appearing only during IMG (e.g., the SW) indicate that IMG requires/involves different cognitive functions/processes to those in INT. The analysis and previous results allowed the discrimination of representative musical styles from different periods which receive a different cognitive learning in the musicians’ life.