Yes, songs are great. It's kinda like anime/manga. Everywhere you go people say you shouldn't use anime/manga for learning, because they either are extremely rude, or overly polite, or that no one talks like that in real life, or whatever argument. The things is, you can totally use it, you just need to have common sense. I really doubt that any serious learner would think that they are a good depiction of the use of the language, or that they should imitate it.
Songs are even less problematic. You still need to have common sense. I'm not going to listen to
Asriel hopping to learn anything other than gothic shit and weird metaphors. And even if I try to get vocab from it, I know better than to use it seriously in my day to day life. I'm not some 12 year old kid that is obsessed with Naruto and try to use juutsus with my tomodachi to improve our kizuna. I'm not going to tell my boss that I can't go to work today because "The crimson blood moon cries tears of sorrow, and thus it signals my fate is intertwined with the threads of the lord of the 4th Hell Circle, which makes my right arm burn with the deepest flames of hell". And of course normal songs are not representation of "normal" Japanese. Poetic language, use of metaphors, I have yet to see a song that don't use 倒置法. But that doesn't matter, there are still lots of benefits for using them.
Obviously there's vocab. There are stuff that doesn't appear as frequent in other media, but there's also a lot of creative use of vocab trough metaphors, expressions, slang, or even vocab with meaning that doesn't come up as often. The interesting is the grammar tho. Songs are grammatically correct. In any language. Well, generally. They might not be what is used day to day, but they are correct. And it's interesting to see how they play with it. You might even learn some uncommon usage of a grammatical point, or maybe even make some sense of some grammar due to a weird usage in metaphors or whatever.
But above all else they are fun. It's fun to listen to them. It's fun trying to dissect the lyrics. I'm always listening to music (a lot of what I listen to is Japanese and it was the little spark that made me decide to learn jgo), and even if I'm not actively listening and trying to understand, it's still helpful because I get more familiar with them, the lyrics get clear and clear, and I often get the urge to sing along. My listening got better for it. I still don't understand much because my overall ability with the language is pretty poor. I was SUPER stoked when I was listening to androp's
Nam(a)e (casually, not paying a lot of attention), and kinda understood the first verse, and I was like "wait, what. Did I hear what I thought I heard?" and went to check out the lyrics and search the vocab and grammar I didn't know, and I got the overall meaning right. Or how the first couple of times I watched indigo la End's
幸せが溢れたら MV, didn't understand what that dialog, tried to translate the lyrics later, got the overall meaning, forgot half of the stuff (every time, I go look at what しどろもどろ is, and I always forget), thought I understand what it meant. Then recently, I went back to it I understood the dialog, even thought I can't hear what she's saying in the middle (I understand いろんなこと○○は忘れたち, not sure on the たち tho), and it changed my understanding of the song from "They were childhood friends (for some reason the first two verses made me think of that), were super close, started dating, the guy did something bad and ran away, time passes, he sees her, remember of the past, sees how he still loves her, but it's too late, she is basically 'You're dead to me' and stuff", to "They were a couple, she has a diseases that makes she forget stuff (Alzheimer or something I guess, not well versed on these things), because of that the guy left her, and when he sees her much later she don't remember him, yet he does and still loves her." Or, last example, how I learned that cellular division is 細胞分裂 trough きのこ帝国's
夜鷹 (and also that nightjars are a thing), tho I can't even pretend to understand what the song is about.
Shit this got bigger than I planned.
(PM if you need to concerning this! Thanks!).
