This paper presents an investigation of age and friendship effects on the processes and outcomes of children's musical collaborations. Previous research in this area (Miell and MacDonald, 2000) has highlighted that when children work together with a friend they produce compositions that are rated as being better quality than compositions produced by children who do not work with a friend. In addition, children working with a friend have been shown to communicate (both verbally and musically) in a style that is more conducive to good quality collaboration. In the present study, girls worked together on a keyboard composition, and pairs of different ages were compared since the effect that age might have on children's compositions is currently a topical issue (Barrett, 1998). All verbal and musical communication was coded in line with criteria developed and validated previously. The younger girls who worked with a friend produced compositions that were rated as being of a better quality than the compositions produced by those of the same age who did not work with a friend. In addition, the musical and verbal interactions of these friendship pairs were seen as being more characteristic of good quality collaboration. This effect was not found for the older pairs, and possible reasons for this pattern of findings are discussed.