Is

Is

Interestingly in the UK, we would say ''Which' answer is correct'? And we wouldn't necessarily use the word 'playing', either - as the loudness or volume mentioned tells us it is playing. So, as a native Brit I would say, 'The Christmas music is very loud.' But since language changes and is prone to regional and other variations - and here these discrepancies make useful examples of how it shifts and sways - rightness and wrongness are tricky to actually quantify. Language is also prone to both objective and subjective shades and styles. Personal influence is huge universal rules are at their mercy. Rather like opinions on a sunset there are changeable, variable and open to context: they shift around.