He says that to reason about just distribution of a thing, we have to reason about, and sometimes argue about, the purpose of the thing, or the social activity -- in this case, musical performance.
On kaže da kada prosuđujemo o pravednoj raspodjeli neke stvari, moramo prosuđivati, i ponekad se prepirati, o svrsi te stvari ili društvene aktivnosti -- u ovom slučaju, muzičke izvedbe.