Bass players would do well to read and understand the section for guitarists. (Review Guitar Theory). When you are just beginning, you can leave all the minors and 7ths to the guitar players. Your job is to hit the bass, and alternate bass notes for each chord. The circle of fifths is your guide. Here are two bits of information that will be specifically helpful to you as a bass player.
1. The four strings on your bass have the same names as the lowest four strings on a guitar. But yours are an octave lower.
2. Your instrument is set up in such a way that learning where to find your notes is fairly simple.
Your strings are E, A, D, G. Does that look familiar? (Look at the circle of fifths.) If the guitar is playing a D chord, you can alternate between D (on the downbeat) and A (on the off beats). Always. You can go from your bass note to the same position on the string below it and back again. If you are playing a C (it’s located at a certain point on the A string), you can go to the same finger position on the string below A (the E string) for your alternate bass note. G’s alternate is D. And the alternate for F# (found on the D string) is the same finger position on the A string.
Once you can keep yourself (and your band) going with bass and alternate notes, you’ll want to learn how to “walk” from one note to another. When the time comes, it won’t be hard at all if you’ve got the basics down really well. If you are a real beginner, see if you can get someone to put tapes on the neck of your bass to indicate finger positions. The tapes should go where the 2nd and 4th frets would go if it were a guitar.
To walk up from an A to a D, play: A, B, C#, then D. To walk down, just reverse the order. The notes of this “walk” need to be played twice as fast as your bass and alternate bass notes. There’s no real substitute for having someone show you – and then just trying it.
There are many more really great mathematical relationships that will help you understand more and more what you are doing. But take this beginning stuff and run with it. It’s quite an adventure!