Halliday & Matthiessen (1999: 171):
… when some element that has functioned as Range is carried through the discourse, being picked up either by a lexical repetition or by a pronominal reference, it is more likely to be picked up as a class, rather than as individuated:Sharon plays tennis at the same time every day. … Tennis is a wonderful game, but tennis players tend to be obsessive.Peter spends a lot of time at the piano. … It is a difficult instrument.