How do you say are you playing in Japanese?

"are you playing" in Japanese can have many meanings.

i.e. Are you playing in the park? = koen de asondeimasuka

Are you playing the Japanese Flute? = shakahachi wo futteimasuka

so it depends what or where they are playing

play = asobu (as in child's play)

play = fukku (if its a blowing instrument your playing)

play = hikku (if its a stringed instrument)

play = yarru (if its football your playing) futtboru wo yarimasu