anime songs have so much detail in the instrumentals, I just didn't know what to do though.
I totally get you on that, both muscially and artwise. Before posting I listened to a couple of my favourite anime songs to see what the music was like, and it's just a blur of stuff, I couldn't tell anything that was going on at all :P
Adding details in art is a similar thing - you can see it in other peoples work but you just can't figure out how to add it to your own.
I can't sing hardly at all :P
I record myself occasionally to see if I've gotten any better and, typically, I haven't :P
keep it up :)
maybe have you tried copying a favourite song (not necessarily all of it) as much as you can , and then compare the results to see how it differs? It's very useful with art and I wonder if that can translate to music.
learning to analyse music is probably very useful in this regard, both just researching what instruments/settings/notes an artist used, but also training your ear to recognise it yourself.
A phrase that I have when analysing artists is "Why didn't I think of that?", trying to figure out my own thoughts(or lack thereof) and finding what thoughts I "should have had" to lead to that artwork that I really like. So not just casually kicking yourself "why didn't I think of that", but really "actually what is the reason why didn't I think of it?"