Learn Hardcore Korean: seojjok bokdo-eseo eumak soriga deullyeo.

In Korean, subjects can be omitted when they are clear from context. Here it’s obvious the speaker is the one hearing the music, so you don’t need to say 나는 or 내가.

What does the particle 에서 do in 서쪽 복도에서?

에서 marks the place where something happens or originates. In this sentence it indicates “in/at” the west corridor as the location the sound comes from.

Why is 소리 followed by 가 in 음악 소리가 들려?

Korean uses the subject particle 가 to mark “sound” as the subject of 들리다 (to be heard). So literally it means “the sound of music is heard.”

What’s the difference between 듣다 and 들리다?

듣다 means “to listen” (active: someone listens to something). 들리다 is the passive/intransitive form meaning “to be heard” or “to be audible” (the sound comes through to the listener).

Why is the verb form 들려 used here instead of 들려요 or 들립니다?

들려 is the plain (informal) present tense of 들리다. If you want to be polite you can say 들려요 (casual polite) or 들립니다 (formal polite).

Can you omit 소리 and say 서쪽 복도에서 음악이 들려? Does that change the nuance?

Yes, 서쪽 복도에서 음악이 들려 is also fine and means “I can hear music from the west corridor.” Adding 소리 simply emphasizes “the sound of music.”

How would you ask “Can you hear music from the west corridor?” in Korean?

In casual speech: 서쪽 복도에서 음악 소리가 들려?
In polite speech: 서쪽 복도에서 음악 소리가 들려요?

How do you express this sentence in the past tense?

Change 들려 to 들렸어 (casual) or 들렸어요 (polite):
서쪽 복도에서 음악 소리가 들렸어.