I do not think anyone has told you
what the difference is.
Until you start getting lead breaks, which will be several years down the road, you play the notes of the active chord in the song. One note at a time. That's the difference.
Which notes? Start with the root note, if you have room bring in the 5 (R-5-R-5) Still have room the 8 is always a safe note. (R-5-8-5). That one generic R-5-8-5 will let you play a lot of bass. Later on you will want to bring in the correct 3 and 7 into your bass line.
I use the major scale box pattern and fake chord sheet music. Practice the following chord tone patterns the same way you did your major scale on the 6 string guitar. For example; Dm chord coming up and your fingers know what notes (or scale degrees) make up the Dm chord. Once you have that in muscle memory all you have to tackle is how many of those chord tones will be needed in this specific song.
Major Scale Box.
Code:
G|---2---|-------|---3---|---4---| 1st string
D|---6---|-------|---7---|---8---|
A|---3---|---4---|-------|---5---|
E|-------|---R---|-------|---2---|4th string
The Cmaj7 chord is coming up. Place the box's R over a C note on the 3rd or 4th string of your fretboard then play the chord spelling of a Cmaj7 chord. That is the R-3-5-7 scale degrees of the C major scale. Start with just the root note and then bring in as many other chord tones as the music will allow before it goes off and leaves you.
Basic Chords
• 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
Place the box's R over the Root note of the chord you want to play over.
Any note's 3rd is up a string and back one fret.
Any note's 5th is up a string and over two frets.
Any note's 7 is up two strings and over one fret.
I catch the b3 next fret from the 2 and the b7 is up two strings, same fret as the root.
Something that gets overlooked; Your basic chords are made of the root, three, five and seven notes in the roots scale. Find the root and the 3 is always up a string and back one fret. The 5 is up a string and over two frets and the 7 is up another string and over one fret. The b3 is one fret over from the 2 and the b7 is right over the 4. Always in the same spot. So find the root and the rest is just knowing how to find the other chord tones. Using this method you can "see" chords all over your fretboard.
Now that is the difference in the way a bass player thinks. Will take a little getting used to, but, the box pattern, fake chord sheet music, and knowing how you can get to the first 7 notes of any scale take a lot of the stress out my life. If this makes since, help yourself.
www.studybass.com will be a friend.
Be sure to spend some time here.
http://www.studybass.com/study-guide/
I think this may turn on a light bulb.
http://www.studybass.com/lessons/common-bass-patterns/common-patterns-summary/
Be sure to check out the exercises at the end of each section.
http://www.studybass.com/lessons/common-bass-patterns/common-patterns-summary/exercises/
Have fun.
I wasn't quite as lucky.
