I'm not Chinese so this could be incorrect, but I don't think 好好 forms imperatives. 好好 is an adverb that just means "well," or something close to that. It can sound like an imperative if there aren't other words in the sentence, but I think you could also use that phrase in a non-imperative sentence like 如果我好好学习，我就成功 (If I study hard, I'll succeed). People often also say 好好保重你自己 which means "Take good care of yourself" -- even though this sentence happens to be an imperative, the 好好 part just emphasizes to take "good" care of yourself. Again, I could be wrong, but I think an imperative in Chinese is formed just by saying any verb by itself in the right context or situation. If you add 吧 after a verb it is a softer, gentler way of making an imperative, or at least that's how it was explained to me.

Normally, if you add "好好" before the verb, that means you will do it hard. But it isn't done. And people usually put some words like "要" before the "好好". It make the sense more clearly.

I think you better use 最 我最喜欢音乐

yes, everything helps, Massimo! Thank you very much! :D

It sounds more like " you had better " , can also refer to an order ,but grammatical ly ,it is not imperative . Here is my personal opinion ,I hope it helps :)