Arrangements: flexibly adapting music data for live performance

Human-Computer Music Performance for popular music – where musical structure is important, but where musicians often decide on the spur of the moment exactly what the musical form will be – presents many challenges to make computer systems that are flexible and adaptable to human musicians. One particular challenge is that humans easily follow scores and chord charts, adapt these to new performance plans, and understand media locations in musical terms (beats and measures), while computer music systems often use rigid and even numerical representations that are difficult to work with. We present new formalisms and representations, and a corresponding implementation, where musical material in various media is synchronized, where musicians can quickly alter the performance order by specifying (re-)arrangements of the material, and where interfaces are supported in a natural way by music notation.