Hello! I'm new on this site, I'm not quite sure that this post belongs on this forum, but I'll give it a shot. I was given a bass around a year ago, I started practicing by readings tabs on the net and playing with songs. It was not until recently that I took bass playing seriously, I tried learning a little theory through web sites and books. I haven't taken lessons yet, so I really don't know much. I have a couple of friends who play guitar, and we've recently tried writing our own stuff. I was wondering if anyone could give me a few pointers regarding bassline construction? I've read the article on that subject on this site, but I still have a few questions. So far I know that when you write a bassline, you can use the root notes of the given chord, and throw in some leading tones, in order to make the bassline sound more melodic, interesting. My question is, do these leading tones have to be chord tones(of the given chord) or scale tones(of the given key)? Can notes out of the given chord and scale be used? If so, in what circumstances? Another problem that I've run into is, the guitar players I play with have little or no knowledge of theory(they know less than I do, which is next to nothing), so the way we attempt to write songs is by laying out a chord progession. But to my understanding, the correct way to write a song, would be to choose a certain key, and then determine which chords are to be used. So my problem is, the guitar player gives me a chord progession, then I try the target and approach method to come up with a bassline, I know I'm going to be safe using chord tones and scale tones for the leading tones, but because I don't know what key the song is in, I don't know what the scale tones are! And that's frustrating, because I know it's going to limit my choice of notes for the bassline! Here's my next question, how do I figure out the key of the song with a set of chords? Lets say the chord progression is E-G-A-D, what's the key of this tune? I was also wondering what other ways can you write a bassline besides using root notes and leading tones? I would really appreciate it if someone can help me out! Thanks for reading!