I found Online Bass Lessons at StudyBass.com and Ed's book "Building Walking Bass Lines" to be on track and both have great value. There is one more bass line book I would recommend, "Bass lines in minutes" by Kris Berg. "Bass Guitar for Dummies" is a good refresher book, as it has a little bit of everything you will be using. Your public library will probably have a copy.
My old standby chart of generic bass lines using the major scale box as a Rosetta stone may help:
Bass Patterns based upon the Major Scale box.
Code:
[B]Major Scale Box[/B].
G|---2---|-------|---3---|---4---| 1st string
D|---6---|-------|---7---|---8---|
A|---3---|---4---|-------|---5---|
E|-------|---R---|-------|---2---|4th string
Basic Chords Have a C major chord coming up. The root, 3rd and 5th scale degree of the C major scale is what needs playing. Have a C minor chord coming up - the root, flatted 3rd (b3) and the 5th scale degree is what is needed to play the Cm chord. Find a C note on your fretboard, place the major scale box's R on that C note and play the R-3-5 scale degrees from the box. For the rest of the story, read on.
• Major Triad = R-3-5
• Minor Triad = R-b3-5
• Diminished Chord = R-b3-b5
7th Chords
• Maj7 = R-3-5-7
• Minor 7 = R-b3-5-b7
• Dominant 7 = R-3-5-b7
• ½ diminished = R-b3-b5-b7
• Full diminished = R-b3-b5-bb7
See a chord and play it's chord tones. As every key will have three major, three minor and one diminished chord it's a good idea to get your major, minor and diminished bass line chord tones into muscle memory so when you see a chord your fingers just know what will work. Think of those R-3-5-b7 being little scales, practice them like you did your scales. Get the scale degree pattern for the major, minor and diminished seven chords into muscle memory. Now the song may only give you enough room for the root, or root five - adapt and get as many chord tones into your bass line as needed. Root on 1 and a steady groove from the other chord tones plus something to call attention to the chord change will keep you gigging.
Scales
• Major Scale = R-2-3-4-5-6-7 Home base
• Major Pentatonic = R-2-3-5-6 Leave out the 4 & 7
• Natural Minor Scale = R-2-b3-4-5-b6-b7 Major scale with the 3, 6 & 7 flatted.
• Minor Pentatonic = R-b3-4-5-b7 Leave out the 2 & 6.
• Blues = R-b3-4-b5-5-b7 Minor pentatonic with the blue note b5 added.
• Harmonic Minor Scale = R-2-b3-4-5-b6-7 Natural minor with a natural 7.
• Melodic Minor Scale = R-2-b3-4-5-6-7 Major scale with a b3.
Let the major scale be your home base then change a few notes and you have something different. No need to memorize a zillion patterns. Let the major scale pattern be your go to pattern - then adapt/adjust from there.
Generic Notes - for your bass line.
• The root, five and eight are generic and fit most any chord. Remember the diminished has a flatted 5. So R-5-8-5 is going to be a safe bass line for everything except a diminished chord.
• The 3 is generic to all major chords. So R-3-5-3 will fit under any major chord.
• The b3 is generic to all minor chords. And R-b3-5-8 will fit under any minor chord. Why the 8? Well the 8 is just another root in the next octave.
• The 7 is generic to all maj7 chords. Yep, R-3-5-7 fits nicely.
• The b7 is generic to all dominant seventh and minor seventh chords. G7 = R-3-5-b7 or Gm7 = R-b3-5-b7.
• The 6 is neutral and adds color, help yourself to 6’s. Love the sound of R-3-5-6 with a major chord.
• The 2 and 4 make good passing notes. Don’t linger on them or stop on them, keep them passing.
• In making your bass line help yourself to those notes, just use them correctly.
• Roots, fives, eights and the correct 3 & 7 will play a lot of bass.