Translation:Do you listen to music?
More literally translated this sentence would be "About music, do you listen to it?". Music is the topic, not the one you're talking to. You can also use を, that would change the meaning to "Do (you) listen to music?".
But because the literal translation of the sentence with は sounds strange in English, you translate it just like the one with を.
I thought so as well, at first, but "music" would usually not be topic in that case -- it could, of course, but it usually wouldn't, and therefore adding it would be more confusing than not.
Unless the developers simply haven't thought of it yet, in which case reporting it might help.
The topic is not a sentence component in the same way as subjects, objects ect. Something can absolutely be the topic and the subject/object/adverbial at the same time. In fact that is very often the case. For most case particles, the topic marker -は would simply be added after it (for example if がっこうに “at/to the school” is topicalised, it becomes がっこうには). The subject marker -が and the object marker -を are exceptions to this: They simply get replaced by -は. So you could think of おんがくは in the above sentence to actually be おんがくをは on the deep structure, only the -を got eaten by -は.
So the topic particle おんがくは聞きますか is not a mistake, it’s a perfectly valid variation on おんがくを聞きますか.
"Do you listen to music" is marked as incorrect, instead it should be translated as "do they listen to music". Since I waste my time trying to learn Japanese with Duolingo I wonder how Japanese language makes clear the difference, how should I know that? Even now it is not clear what mistake I have made, so should I first take a course in Japanese elsewhere and then start with Duolingo here?
I would avoid using Duolingo to learn Japanese seriously at the moment. There are a lot of little things right now that are not quite right and could solidify bad habits if you don't realize it. There is a little bit of a "blind leading the blind" problem right now, though I don't want to disparage the efforts of those working to improve the system.
How come the other sentences like this translate to "are you writing a letter" and "are you watching a movie" but then in this case, "are you listening to music" is wrong? i understand there is another way of saying you are presently listening to something, but then how come it's not the same for the other very similar questions....like the watching of movies and writing of letters?? It's not consistent and I don't understand why.
"will you listen to music" to me suggests either "will you want to listen to music now" if so would be "音楽が如何ですか" (ongaku ga ikaga desu ka) or "are you willing to listen to music" which would be conjugated differently (probably along the "聞いてもいいですか" (kiite mo ii desu ka) lines). It doesn't have the same meaning as the japanese phrase in question...
It probably plays not only 聞 but 聞き because 聞 is not even the complete stem of the verb. That’s kik-, with the consonant but not the vowel of the second syllable – this is why the vowel changes in different verb forms: 聞く, 聞きます, 聞かない, 聞け…
Another possible reason is that the computer might use a different reading (ぶん or もん) if you told it to read just 聞 without an ending that shows the verb is meant.