Terry Santos answers:

Actually, guitars, like catfish, don't HAVE scales. Bluegills have scales, just like your bass.

Terry Santos answers:

You improvise by following the chord progression of the song. As the chords change, the scale pattern you are improvising with changes. What type of scale you would want to use would depend a great deal on the song itself and specifically the chord progression and complexity of the chords used.. I say scale pattern because you do not want to play scales in an improvision. When you do that, you just sound like you are practicing. Learn the scale patterns and the notes in all of the chords and from that you will instinctively know how to improvise and what scale pater is best for what chord and progression. It would help if you have a good chord book like the Hal Leonard Picture Chord Encyclopedia.

Terry Santos answers:

A good way to improvise is to play the scale of the "I" chord of the key you are in.(Lets say Blues Scale)....

Play the 1st note.
Then the 1st 2nd 1st.
Then the 1st 2nd 3rd 2nd 1st.
Then the 1st 2nd 3rd 4th 3rd 2nd 1st.
Just keep it going like that....

Blues Scale-
1st, flat 3rd, 4th, flat 5th, 5th, flat 7th, octave.
---------

So play......

1st, flat 3rd, 4th, flat 5th, 4th, flat 3rd, 1st.

1st, flat 3rd, 4th, flat 5th, 5th, flat 5th, 4th, flat 3rd, 1st.

1st, flat 3rd, 4th, flat 5th, 5th, flat 7th, 5th, flat 5th, 4th, flat 3rd, 1st

1st, flat 3rd, 4th, flat 5th, 5th, flat 7th, octave, flat 7th, 5th, flat 5th, 4th, flat 3rd, 1st.....

After you get that far, include higher and lower octaves.

Experiment with rythmic patterns such as throwing it over a Shuffle, Rhumba, or a swing. This should give you hundreds of improv ideas.

Terry Santos answers:

There are a lot of books and other media on scales and their relation to chords. I play bass and have been struggling with this same issue for year. It boils down to knowing theory. This link to a guitar forum has some great insights and suggestions:
http://www.guitarnotes.com/forum/ultimatebb.cgi?ubb=get_topic;f=20;t=000121

Terry Santos answers:

Dr X's answer is correct but maybe you need to understand the theory more. A scale is the path you take through an octave (like from a C to a high C). Start from any note; if you go up just one fret, that's a half-step (like C to C#, 3rd to 4th fret on your A string). If you go up two frets, it's a whole step (like C to D, 3rd to 5th fret on your A string).

With "w" for whole steps and "h" for half steps, a major scale goes wwhwwwh. A minor scale goes whwwwhw. Try doing that on just one string to start, say your E string:

E major will look like this:
E - 0 - 2 - 4 - 5 - 7 - 9 - 11 - 12

E minor will look like this:
E - 0 - 2 - 3 - 5 - 7 - 9 - 10 - 12

So far so good? Now, as you probably know, the fifth fret on one string is the same as the next string up, played open. That means you can go up the scale without constantly having to slide your hand up the neck.

So you can play your E major scale like this:
G - -------------------------------
D - -------------------------1 - 2
A - ------------ 0 - 2 - 4 -------
E - 0 - 2 - 4 --------------------

Or the pattern Dr. X showed you. Use www.studybass.com, or get a book of bass scales (they're only $10 or so) and it will show you lots of patterns to follow. Once you're comfortable with major and minor scales, you can move on into more complex things like modes and things like mixolydian scales, etc.