If you've played any bass guitar scales you've noticed that sometimes the notes were 2 frets away from each other and sometimes they were only 1 fret away.

See the illistration below...

Each fret on the bass guitar represents, one SEMI-TONE

If you go from 'F' to 'G' a jump of 2 frets, that represents, one TONE.
If you go from 'F sharp' to 'G' a jump of 1 fret, that represents, one SEMI-TONE.

Let's nail down the structure the G major scale.

Now look at a simplified version of the scale showing the intervals between the notes.
The 'T' is one TONE (a stretch of two frets on your bass)
The 'S' is one SEMI-TONE (a stretch of one fret)

Review playing the G major scale...

I've just shown you the secret to the modes, and for that matter all musical scales!
All scales in western music are defined by their patterns of TONES, and SEMI-TONES.

Now you know for all major scales the pattern you play is: T,T,S,T,T,T,S

Start on 'A' and play: T,T,S,T,T,T,S
That's the A major scale...

Start on 'D' and play: T,T,S,T,T,T,S
That's the D major scale...

And so on...

Back to the lesson on modes...

Back to the free bass guitar scales...