Achieving a blended timbre between two instruments is a common aim of orchestration. It relates to the auditory fusion of simultaneous sounds and can be linked to several acoustic factors (e.g., temporal synchrony, harmonicity, spectral relationships). Previous research has left unanswered if and how musicians control these factors during performance to achieve blend. For instance, timbral adjustments could be oriented towards the leading performer. In order to study such adjustments, pairs of one bassoon and one horn player participated in a performance experiment, which involved several musical and acoustical factors. Performances were evaluated through acoustic measures and behavioral ratings, investigating differences across performer roles as leaders or followers, unison or non-unison intervals, and earlier or later segments of performances. In addition, the acoustical influence of performance room and communication impairment were also investigated. Role assignments affected spectral adjustments in that musicians acting as followers adjusted toward a “darker” timbre (i.e., realized by reducing the frequencies of the main formant or spectral centroid). Notably, these adjustments occurred together with slight reductions in sound level, although this was more apparent for horn than bassoon players. Furthermore, coordination seemed more critical in unison performances and also improved over the course of a performance. These findings compare to similar dependencies found concerning how performers coordinate their timing and suggest that performer roles also determine the nature of adjustments necessary to achieve the common aim of a blended timbre.

The Role of Anticipatory Auditory Imagery in musical ensemble performance was investigated by examining the relationship between individual differences in auditory imagery and temporal coordination in piano duos. Vividness of imagery for upcoming sounds was assessed in 14 pianists using a task that required the production of rhythmic sequences with or without auditory feedback. Ensemble coordination was assessed by examining temporal relations between body movements (recorded by a motion capture system) and sound onsets (triggered by key strokes on two MIDI pianos) in seven duos playing two contrasting pieces with or without visual contact. Sound synchrony was found to be related to anterior-posterior body sway coordination in a manner that depended upon leader/follower relations between pianists assigned to 'primo' and 'secondo' parts. Furthermore, the quality of coordination, which was not affected markedly by whether pianists were in visual contact, was correlated with individual differences in anticipatory auditory imagery. These findings suggest that auditory imagery facilitates interpersonal coordination by enhancing the operation of internal models that simulate one's own and others' actions during ensemble performance.