Musical engagement is influenced by both environmental and genetic factors. Here, we explored non-genetic influences on musical engagement by performing semi-structured interviews of 10 Swedish monozygotic twin pairs that were highly discordant for piano practicing. The interviews were organized into five sections – (i) perceived reasons for the discordance; (ii) childhood differences in specific music related variables; (iii) strong memories of music; (iv) the perceived meaning of music in life and for health; and (v) language interests – and analyzed using response categorization. The playing twins from an early age found music more interesting and enjoyable than their co-twins and also gave richer and more elaborate descriptions of the meaning of music in life, in several cases emphasizing that music was important for their personal identity. In line with this, an analysis of previously collected web questionnaire data showed that the playing twins had a significantly higher openness to experience and proneness to experience flow during musical activities. In contrast, the twins reported essentially no within-pair differences in the musical engagement of their peers, parental support, music teacher, ensemble playing, public performances, and their interest and aptitude for languages. The interviews gave no indication that the differences in musical engagement were caused by systematic environmental influences that were consistent across twin pairs. Rather, the respondents presented a wide range of different explanations for their discordance in musical activity, suggesting that the remaining influences on musical engagement, when genetics and family environment are controlled for, may be highly individual and idiosyncratic.