"Do you want to play music now?"
Translation:¿Quieres tocar música ahora?
If specific music or music in the most general sense was implied by the English, then you would include the article la. Otherwise, if it's not in the English, then it's not going to be in the Spanish.
You will encounter English sentences where a definite article is implied, but not stated. You will need to include the article in a correct translation to Spanish. This will make it appear as if Spanish doesn't follow any consistent rules with regard to definite articles. Or, it may make you think Spanish uses definite articles much more often than English. My impression, however, is that Spanish is just more consistent in its use/expectation of definite articles than English. Actually, it's probably more accurate to say that Spanish as practiced on Duo is more consistent. I believe that native Spanish speakers often drop the definite article when it should be used.
Isn´t "escuchar musica" also a valid translation here ? Google translate thinks so, anyway...
Jugar is used to play a game or sport. Tocar is to play music, an instrument.
If you use escuchar you are talking about playing music on the radio or some device rather than playing music with instruments. While that's okay in the sense that the English is vague about how you are going to "play" the music, it probably stretches Duo's ability to drill us on the verb tocar.
You could report it as a valid translation with a particular context in mind. Don't be surprised, however, if Duo still hasn't added that interpretation six years from now.