Even though learning the lyrics of songs does help in learning phrases...sometimes the lyrics may get too deep and complex for beginners. They may use idioms or other expressive language that are not exactly used in normal everyday conversation The best way to learn a language is the environment. Go to a place where they speak the language. But then...obviously not everyone can do that... This is why I actually think watching movies or dramas will help much more in learning a language You get to learn basic phrases in conversation. Even though it's a substitute...it's very effective.

I don't think so. Usually the lyrics are more like poems, most of which are badly made. It's a bit far to both the modern oral and written Chinese. Some of them are really beautiful, but they may be more close to the ancient Chinese, which is not so easy to a beginner, even to many Chinese people. And as a beginner, it's hard to distinguish which song is good and proper. So, I think it's better to speak with local people and read common books.

I think the best way is conversation

Yes, movie is better than music in my opinion, espesical simple situation comedy about modern society like "家有儿女'

How would learning, lets say, playing erhu, help with learning a language? Lang Lang plays Beethoven well and doesn't know a word of German.