You can say it either way.

You need to know how to use it both ways. It's a bad idea to "economise" your use of English before you fully understand it. Here's another thought: if you hear native English speakers say "one of my friends", why do you want to say something else? I'm sure that you want to sound as native as possible. :)

"I've listened to it before because one of my friends loves it." = "I've listened to it before because a friend loves it" > these are ok. But, the word "because" needs to be clarified . Its too vague . Are you saying that whatever your friend like , you would have heard it ?? Are you saying that just because your friends likes it , you have to listen to it? Make it clear . "I've listened to it before because a friend ,who likes it , recommended it to me"

Thank you very much for your opinion, Kevin.

I don't feel either sentence is more correct than the other. It's more natural for me to use "...one of my friends..." rather than "... a friend..."; however, I'm sure I've both at one time or another. Hope this helps! Cheers! -Kevin