Translation:What music do you listen to?
The English translation you mean? It is unnatural, and not technically correct English (I was a bit irritated to see Duolingo use incorrect English as the "answer"). But people speak that way in casual use. But heaven help you if you end a sentence with "to" in front of an English teacher lol
"What music do you listen?" is incorrect; however, "What music do you hear?" would be correct. When "to" follows the verb "listen," then the verb can take an object, namely, "music" in this case; whereas, "hear" can take an object by itself: "I like to listen to the birds singing," versus "I like to hear the birds singing."
English distinguishes between "hearing" and "listening." You may "hear" music that just happens to be playing in the background, but to "listen to" music requires deliberate concentration on your part: you are not just "hearing" music as you dance or drive or work, for instance, but actively "listening to" music to enjoy how the musicians are interacting, or to learn the lyrics to the song, or simply because you enjoy the activity of listening to the music itself.
歌 is "song" and 音乐 is "music."
音乐 is music in general, any music.
歌 is song in particular, such as choral or vocal music, music produced by a voice, or a specific musical composition, generally brief, maybe just a few minutes long, and generally simple enough to be performed by just a few musicians, or even by a single musician.
Not all music is song. A chord progression, such as a 12 bar blues progression or the "Rhythm Changes," is music, a musical "template" if you will, that does not become a song until someone adds a melody to it. The background music in a movie, "incidental music," or "mood music," is a type of music, but not always a song. Beethoven's 9th Symphony is not "a song," but someone could sing the choral finale as a song.
音乐会 = concert
音乐学 = musicology, the study of music, music as a subject of study
民间音乐 = folk music
爵士音乐 = jazz
音乐院 = conservatory, college of music
音乐家 = musician
国歌 = national anthem
山歌 = folk song, mountain song
民歌 = folk song
歌唱 = to sing
歌唱家 = singer
歌星 = singing star, famous singer
歌词 = song lyrics
Hi TsukiyoAlex, "musics" is not really correct in English with the exception of very rare cases in academic writing about music, where famous authors will sometimes invent words or uses to explain complex topics. You will never hear "musics" spoken by a native speaker, at least in American style English (I am not qualified to comment on British English).
An-duo-crates, I think your answer captures the sense of the sentence. That being said, in language learning with a teacher or an app, it's good to get in the habit of being super literal, not only because the app won't accept it but also because it will help you learn better. The reason is that you might start confusing the word for "like" and for "listen" if you translate loosely.