Both singing and playing instruments in a group have been described in narratives as activities that increase cohesiveness. It has been speculated that music making is at the core of cultural activities in the history of humans. Music, dance and religious rituals including visual arts may have arisen because it was necessary to create strong and reliable bonds in a group, and such activities were effective for achieving this goal. This may even have increased chances of survival in life-threatening environments and this may still be true.  According to our study of the Swedish Twin Registry, there is a clear relationship between total number of music practice hours in life (particularly ensemble practice) and ability to handle emotions. In monozygotic twins who are within-pair discordant with regard to piano-playing (one twin has practiced piano extensively and the other not) it has been shown that the size of the corpus callosum, the bridge between the right and the left hemispheres, is larger in the playing twin. Since corpus callosum is important not only for coordination of muscles in the right and left halves of the body but also for emotional skill this is of particular importance – music training may stimulate parts of the brain that govern emotion handling. During performance, strong group interactions can occur both within a music ensemble and between the ensemble and the audience. In our group we have an ongoing project MUSETHICA that examines biological, psychological and social processes when one ensemble plays the same piece in front of different audiences. Accordingly, the audience reaction is studied by means of visual analogue scales, group flow in the ensemble by means of a standardized questionnaire (flow synchronization scale) and heart rate variability on line (for the assessment of sympathetic and parasympathetic balance) during the concerts in all the members of the ensemble. Qualitative interview data focusing on perceived performance quality, group flow and support are collected. Results from a feasibility study will be presented. A string quartet whose young members are going through the advanced training program MUSETHICA for chamber music is performing the same quartet (Haydn opus 76 number 2, D minor) on two occasions the same day with two different audiences of school children aged 13-15. Despite the small size of the study sample the analyses of heart rate variability show that there was a borderline significant variability across the different movements on the two occasions with regard to parasympathetic (high frequency power) and sympathetic (heart rate) activity – with evidence of low sympathetic and high parasympathetic activity during the second occasion during the playing of movement 2. The children showed more uniform reactions on the second occasion according to VAS ratings. The feasibility study shows that it is practically possible to study these complex interactions and that the joint methodology has the potential of showing interesting processes related to group playing.