A Music Theory Primer

For bass players and guitarists.

By Nick Delonas

Musical Notes

There are twelve musical notes. If you start with the low E string on your instrument the notes going up the neck are as follows:

Notes using sharps (#)EFF#GG#AA#BCC#DD#E
Notes using flats (b)EFGbGAbABbBCDbDEbE

Some notes have two names. For example, the note at the second fret is both F# and Gb. It's not important why this is so. Just remember that the note between F and G can be thought of as either F# (F sharp) or Gb (G flat).

The E at the 12th fret is one octave higher than the E of the open string. After that, the cycle repeats with F again following E and so on.


Scales are the basic building blocks of music.

The primary scale that has no sharps or flats is the C major scale. Using the basic scale with no sharps or flats, however, we can build seven scales often called modes.

Number1234567 9 11 13  
Scale starting on this noteMajor (Ionian)DorianPhrygianLydianMixolydianMinor (Aeolian)Locrian        
Triad chordCDmEmFGAmB diminished        
Associated four-note chordCmaj7Dm7Em7Fmaj7G7Am7Bm7b5        
NomenclatureTonicSupertonicMediantSubdominantDominantSubmediantSubtonic (leading tone)        
Chord FunctionTonicSubdominantTonicSubdominantDominantTonicDominant        
Avoid notes by degree in chord scale462, 6none462
Key of C avoid notes by name in chord scaleFBF, CnoneCFC

Knowing the nomenclature of the steps in the scale is not important. I only included it because people often use the terms tonic and dominant when talking about chords. A dominant chord is simply the chord starting at the fifth position in the scale and is usually a chord with a flatted seventh (of its major scale). Thus G7 is typically referred to as a G dominant seven chord.

The tonic or root chord is simply the chord at the starting note in the current scale or key.

The number in the scale is simply where the note is placed. Some notes have different numbers by convention when used to indicate tensions in the dominant version of chords. The dominant version of a C chord (C7) would be the notes C-E-G-Bb. For example, if you add a D to a C7 chord, the convention is to notate it as C9 (C-E-G-Bb-D). If you added an A, that would be a C13 (C-E-G-Bb-A) chord.

The conventions can get a little confusing sometimes, but this is the basic idea. If, for example, you don't use a dominant version, you might see something like Cmaj7 add 9 or Cmaj9 (C-E-G-B-D). If there is no seventh and you add the A, you'd generally see it written as C6 or Cmaj6, which incidentally contains exactly the same notes as Am7 (C-E-G-A or A-C-E-G).

The scale starting on a note means the seven notes starting from that position. So starting at G, the notes are G, A, B, C, D, E and F. This would be the Mixolydian scale or mode, which you can play over a G7 chord. Obviously G Mixolydian is the same as C Major (or Ionian), only the notes of emphasis are different. For example, playing over a G7 chord, you might want to emphasize the notes of the G7 chord which are G-B-D-F.

Still, the C major scale will, in general, "work" over any of the associated chords of the scale (Cmaj7, Dm7, Em7, Fmaj7, G7, Am7, Bm7b5).

You build chords from the scale simply by skipping a note between the notes. So C is just C-E-G (you skip D and F). If you go up one more skip, you add the seventh, which adds some harmonic richness to the sound of the chord. C-E-G-B is Cmaj7.

In the key of C, you can always substitute a Cmaj7 chord where the song calls simply for a C.

The chords associated with the major scale are:

Imaj7 (major 7), IIm7 (minor7), IIIm7, IVmaj7, V7 (dominant 7), VIm7, VIIm7b5 (minor 7 flat 5)

An important concept to remember is that scales and associated chords are determined by the distances between notes.

The major scale is a series of whole steps (two frets) with a half step (one fret) occurring between notes III and IV and between notes VII and VIII (or I).

In the C scale, those half steps occur between E and F and between B C. All other degrees of the scale have a whole step between them. For example, the distance from C to D is two frets with C# in between.

So to create the same set of intervals (distances between notes) in the key of G, we need to raise the F a half step to F#. Otherwise, the G scale would be Mixolydian rather than G Ionian (major).

Note that the distances between the notes is the same for all major scales.

Distance from previous noteHalfWholeWHWWW
D majorDEF#GABC#
A majorABC#DEF#G#
E majorEF#G#ABC#D#
B majorBC#D#EF#G#A#
Bb majorBbCDEbFGA
Eb majorEbFGAbBbCD
Ab majorAbBbCDbEbFG
Db majorDbEbFGbAbBbC
Gb majorGbAbBbCb (B)DbEbF
Scale number1234567
Chord FunctionTonicSubdominantTonicSubdominantDominantTonicDominant
Scale starting hereIonianDorianPhrygianLydianMixolydianAeolianLocrian
Avoid notes by degree in chord scale462, 6none462
Avoid note in key of CFBF, CnoneCFC

You may on rare occasions see chord positions written as I, ii, iii, IV, V, vi, vii. In such cases, the correct chord form (major or minor) is assumed.

Chords that share the same function may sometimes be substituted for each other.  In general, Tonic chords are restful and stable, with the I chord being the most stable.  That's why most songs end on the I chord.  Subdominant chords have a tendency to want to move to either a Tonic or Dominant chord.  Dominant chords have a very strong tendency to move (want to resolve) to a Tonic chord, usually the I.

The avoid notes I listed are notes that either sound dissonant if held against the associated chord or which confuse the function (tonic, subdominant, or dominant) of the chord.  So, for example, you should not normally hold or rest on the 2nd and 6th degrees of the phrygian scale when you want the IIIm7 chord to both sound consonant and function as a tonic chord in the song.  These notes can, however, be used as passing tones -- that is notes that you neither stress nor hold against their associated chords for very long.  


Given a basic chord sequence, you can substitute other chords to add interest to a piece. Just what does and does not sound good depends on the style of music you're playing. The bottom line is: use your ears and decide what sounds good to you. There are no absolutes regarding what are right and wrong notes.

In general, you can substitute chords that are similar sounding. For example, you can generally substitute a IIm7 for the V7. So Dm7 substitutes well for G7 or G in the key of C. If you think about the G7 chord, the most important tones are the root G, and the so-called leading tones B (3) and F (b7). These are what give the G7 its characteristic sound.

The Dm7 chord is D-F-A-C which contains the b7 (F), 9 (A), 11 (C) and 5 (D) of the G7 chord. So if you've got a song in the key of C where there are, say, four beats of G. You can generally substitute two beats each of Dm7 (D-F-A-C) and G7 (G-B-D-F). Or you could try Dm7 moving to Dm6 (D-F-A-B). The 6th note on the D minor chord is simply B, which is the 3rd of G7. So you can, and perhaps should, think of such chord substitutions as a way of playing the same G7 chord, but with tensions that add harmonic interest.

Harmonic "tensions" add to the richness of how music sounds. Again, what does and does not sound good depends on the style of music and on your own preferences.

The most common tensions are the Major 7 and the flatted 7. If the original chord is C you can generally add a B for the major 7 sound (Cmaj7). You can also generally substitute the VIm7, which in this case would be Am7 (A-C-E-G). That is the equivalent (same notes) of a Cmaj6 chord (C-E-G-A), which is another common substitution.

For dominant chords (chords functioning as the V chord in a progression), the seven is flatted. So in the key of F major, the tension on C would be Bb, not B, to form the C7 chord (C-E-G-Bb). You also use a flatted seven on minor chords.

You can almost always simply add a flatted 7 to a minor chord. So you can use Dm7 for Dm, Gm7 for Gm, Am7 for Am, and so on.

You certainly don't have to stick to the scale either. You can add all kinds of tensions for added interest. This works especially well on the V7 chord, which functions as a tension building chord that resolves (releasing the harmonic tension) back to the Imaj7 chord.

For example, instead of G7, you might substitute Dm7 (D-F-A-C) going to a G7b5b9 (G-B-Db-F-Ab) or perhaps a G7#5b9 (G-B-D#-F-Ab). That kind of chord creates a lot of tension that is released when you resolve to the Imaj7 chord, which in this case is Cmaj7 (C-E-G-B).

And just as you can substitute chords, you can substitute scales during improvisation. So if a substitution of G7b5b9 works, then it's safe to assume that hitting the notes of that chord would certainly work during a solo. It also follows that if you build tension in your solo using notes like b5, #5 or b9, that you can release that tension by resolving to a note -- say on the Imaj7 chord -- that is part of the chord. In the case of a Cmaj7 chord, that'd be either C, E, G, or B, with C being the most consonant sound.

So, for example, rather than sticking to a straight Mixolydian scale on a dominant seven chord, you can try flatting or sharping the 5 or flatting the 9. For example, over G7 you could try a scale of G, Ab, B, C, Db, E, and F.

By the way, there are a lot of scales that work with various chords, here are some scales that you can use during improvisation if you run across these chord symbols. 

Chord SymbolImplied Scale
7#11lydian dominant
7#5whole tone
7b9half/whole diminished
altaltered or diminished whole tone
dimwhole/half diminished
Maj #4lydian
Maj #5lydian augmented
Maj b6harmonic major scale
min/Majmelodic minor
min b6 Aeolian
sus b9 Phrygian or 2nd mode of melodic minor

Meter and Time Signatures

Meter refers to how the pulse of the music is grouped. Most commonly the pulse is grouped into four beats (the ol' one, two, three, four).

A time signature indicates the pulse grouping and the kind of note that gets a single beat. So for example, 4/4 is four beats per measure (or grouping) and the note that gets a beat is a quarter note. 6/8 would mean groupings of six beats per measure and the eighth note is a single beat.

For all practical purposes, the bottom note is less important -- drummers have to worry about it more than we guitarists and bass players I guess. It's the top number that definitely does matter to us because that's how many beats you have to count to get back to the ONE beat, where there's typically a chord change.

The most common time signatures are 4/4 and 3/4. 3/4 time signatures are typically used in waltzes. 4/4 applies to all manner of music -- rock, jazz, pop, shuffles, Latin, Motown and so on.

Other time signatures do often show up though. 6/8 is common in African and in Spanish folk music. 9/8 is used in a style called Rampi Greek. 11/8 is common in African music as well.

In jazz and progressive rock, all kinds of time signatures show up. I've seen all of the following in actual songs: 2/4, 3/4, 4/4, 5/4, 5/8, 6/8, 7/4, 7/8, 9/4, 9/8, 11/8, 12/8, 13/8, 22/8 and even 35/16.

Sometimes counting out such meters is difficult, but often you can feel where the ONE beat is once you've rehearsed a song enough. To count a time signature, you count up to the top number and then repeat. So you would count 7/4 as 1,2,3,4,5,6,7, 1,2,3,4,5,6,7, 1,2,3,4,5,6,7 . . . .  Or you could count it as 1,2,3,4,1,2,3, if that's easier.

Another thing you might encounter in jazz or progressive rock is the multi-rhythm or polyrhythm. This is typically where one instrument is playing in one time signature and another instrument in another. For example, the drummer might play a bar of 4/4 while the guitar and bass play a bar of 3/4 in the same amount of time.

Such mixed time signatures can be interesting. Some artists layer multiple time signatures where every player is playing in a different one and the drummer may even be handling more than one.  I've heard multi-rhythms used by a number of popular groups, including Frank Zappa and Led Zeppelin. Just don't ask me which tunes they were on, because I don't remember. I just remember coming across them.

Anyway, I sure hope this page gives you some small insights into music that you may not have already had. Feel free to e-mail me with questions or comments. I might use them to update this page. After all, I'm still learning too.

Happy playing folks!


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