Music Theory
for Guitar and Bass

   This page is not meant for the complete beginner - its for a player who already has some playing skills, who knows common chords, bar chords, is familiar with the note names, and understands octaves.

   The most important concept that you have to grasp to be a musician is this: All chords, instrumental solos, and bass lines,vocal melodies, harmonies, etc in a song will be made up of notes from the scale in the key that the song is in. This is not true 100% of the time there are exceptions - often a skilled player can step outside the scale notes somewhat, however when first learning this stuff it's best to just learn to play inside the scale. It's really not that difficult to understand, but requires practice to learn the scale patterns, commit them to memory, and to develop the physical playing ability and the ear for using them. Playing most popular forms of music doesn't involve reading parts from written music notation, a song is in a certain key and you're given a chord progression(the rhythm guitar part) to play along with. How do you come up with good guitar licks, solos or bass lines to fit? A player without knowledge of scales, harmony and arpeggio's is limited to playing by rote, or playing only the root notes of chords, a musician with the proper music knowledge can create more melodic, interesting lines. Not all music stays in one key - when you're first learning scales it's best to start with music that does (almost any pop, rock, folk, blues or country song, with some exceptions). For pop, folk or country music learn the major scale( the "do, re, mi, fa, so, la, tee, do"scale). For rock and blues its mainly the pentatonic(5 note) blues/rock scale, - however a good number of rock tunes use the major scale(and its modes - more on modes later) as do a small number of blues songs. The following fretboard scale diagrams are applicable to both guitar and bass as the four strings of the bass are tuned to the same notes as the bottom four strings on the guitar, just an octave lower - for bass ignore the top two strings in the diagram.

                                                        Major scale

                                           

The lowest string in the picture corresponds with the lowest pitched string on the guitar, the nut is to the left. The "R" is the root or key. The pattern can be shifted up or down the neck to play in any key, if "R" is at the 5th fret key is A, 3rd fret - key of G,  8th fret - key of C, etc, etc. Commit this pattern to memory, develop finger dexterity by playing the notes, and start using it to play melodies, solos, bass lines or whatever, get familiar with how the notes sound in relation to each other. Play along with a rhythm guitarist or record a simple chord progression in the key of A using A, D, and E major chords and then try playing solos or bass lines along with it. It will sound bad at first but improves with practice - listen to how the notes of the scale sound with the chords. Not all of the scale notes will sound right all of the time. This is just one of the major scale patterns on the guitar fretboard it repeats 12 frets(one octave) higher or lower depending on where you are and there are 4 more in between. Don't try to learn the rest all at once. After learning this one learn either the pattern above this one or the one below. I recommend learning the one below because minor scales are directly related (they use the same notes, but use the 6th note as the root) to major scales and this pattern is the most useful when your learning to play minor key songs. You should be able to figure out for yourself what the other patterns are, once you've got the first one down.

                                    
                                      The Chromatic Scale, Note Names, Major Scales and Chords 

If you play all the notes possible starting at A, there are twelve notes before you hit another A note an octave higher (ie: playing on one string every fret between the fifth fret and the seventeenth fret). This is called the chromatic scale. Its simply a name used to refer to all of the notes.This scale is not often used by itself in music, but small bits of it can momentarily be used, while playing with more common scales, I use it often while playing a blues or jazz rock solo. A commonly used blues turnaround lick uses a bit of chromatic scale. The table below shows the chromatic scale and all the note names, and the relation to the A major scale, then the relation between the A major scale and some common chords encountered while playing in the key of "A". If you're a bass player you might be thinking; why should I learn chords? bass players  don't usually strum chords but play single notes. You should learn chords because bass players frequently play chords by playing the notes of the chord one at a time(arpeggio's). Notice that all of these chords are made up of notes in the A major scale. The notes of the scale are given numbers.  Major and minor Chords are created from using the roots, thirds and fifths in the key of the root note. D major is made from tne root note (D) of course, the third note (F#) and the fifth(A) from the D major scale. This chord can be used when playing in the key of A because all of the notes in it( D,F#,A) are notes in the A major scale. The same relationship applies to the chords listed below. For instance the B minor chord is created from the Root(B), third(D) and fifth(F#) in the B minor scale(more on minor scales later) but can be used in the key of A because all of the chords notes are once again - in the A major scale. Another perhaps easier way of looking at it is that all the common chords in a key can be derived by starting on each of the notes in the scale (this will be the root note from which the chord gets its name), then skip a note then add the next note, skip another note and then add the next one. For fuller sounding chords of more than three notes you can have more than one of each note in the chord - the A major bar chord at the fifth fret has three Roots(A), 2 fifths(D) and one third(C#). There are of course more chords available when playing in the key of A, go ahead -  mix up the notes and make some yourself! 

Chromatic Scale 1 2 3 4 5 6 7 8 9 10 11 12 1
Note Names A A# B C C# D D# E F F# G G# A
A Major Scale R 2 3 4 5 6 7 R
A Major Chord A   C#   E A
D Major Chord A     D F#   A
E Major Chord   B     E G#
F# minor Chord  A   C#        F#   A
B minor Chord   B   D     F#  
C# minor Chord     C#   E G#

 
                                           

Seventh Chords
-  a Major seventh chord is a major chord with a note added that is one fret(or a half step, as its called in music terminology) below the root note of the chord. So from the above diagram you can see that Amaj7 and Dmaj7 chords can be used in the key of A but not the Emaj7 because the note one fret below the E (D#) is not in the scale. You can use an E7 chord because a seventh chord is a major chord with a note added that is two frets( or a whole step ) below the root note of the chord, and that note(D) is in the scale, same goes for minor seventh chords, so Bm7(B minor 7th), C#m7 and F#m7 can be used in the key of A Major.

                                       Solos, Melodies and Bass lines

  When first trying  to create a solo or bass line most players don't do to well at it, the tendency is to play lines that run up and down the scale in a linear fashion starting on the root note of the chord they're playing over. What is often missed is that lines can also start using one of the other notes of the chord - if playing over an A chord try starting your line on the 3rd(C#) or the 5th(E), other notes can sometimes work too -  use your ears. Also, if you keep track of what chord you're playing over you can use bits of arpeggios ( you are playing an arpeggio when you play the notes of a chord one at a time) in your solo or bass line. Use Intervals - if you skip out one note up or down from your previous note the interval jump is a 3rd, two notes - a 4th, three notes - a 5th and so on - you get the idea. Playing arpeggios and intervals is still using scales its just not doing it in a linear manner - look at the fretboard scale pattern near the top of the page - try and visualize different ways of playing through it. Good melodies, solos and bass lines can consist of varying degrees of these elements - linear scale runs, intervals, arpeggios as well as dynamics(playing loud or softly) pauses, silence, noises etc. You need to develop a feel for how the notes, intervals and arpeggio's sound so that you can actually play the things you hear in your head.

                                     Blues/Rock Scale and Minor Scale

                                         

Only one position of the blues rock scale is shown, ignore the black dots for now, they are not notes in the blues scale, they are there to show the relationship of the blues scale to the most common minor scale. Once you learn this pattern you can figure out the other blues scale positions yourself, or find them elsewhere. Once again for the sake of this discussion assume that "R" is at the fifth fret, making it in the key of A, but don't forget you can shift this up and down the neck to play in any key.
   Many simple blues and rock songs in the key of A use the A, D and E major,seventh or ninth chords, but you may notice that the third in all these chords is not in the blues/rock scale. Because of this - often in basic rock, hard rock and some blues, players will use chords that consist of only roots and fifths. The third defines the chord to be either major or minor, so root and 5th chords are ambiguous. The chords you're likely to use or encounter while playing blues scale rock songs in the key of A will be A,D,E,G.C, these will often be chords without 3rds or at least ones where the 3rds aren't prominent. Another, more sophisticated approach to using the blues scale is to add the outside chord tones to the scale while playing over that particular chord. Some simple blues and rock songs have a bass line that does this(Root,3rd,5th,6th,Octave root, then back down) there are lots of variations on this basic lick.
    Sometimes a song will use  only A,D and E chords so you might be unsure which scale to use - either the major scale or the blues scale - just use your ears to tell which one sounds right and go with it. You can play notes outside the scale when doing solos or bass lines but when you're first learning, learn to play with only these notes. once you've got this down good then start experimenting. A common thing is to add bits of chromatic scale between the blues scale notes and, as mentioned above - including into the scale any outside notes in the chord you're playing over.

                                         Minor Scales and Modes

    If you add the black dot notes to the blues scale shown above this makes the natural minor scale, also known as the aeolian minor scale. This is the most common minor scale - there are others. Understanding the relationships between scales is important, and it makes it easier to learn all of them when you see the similarities. This minor scale is directly related to the major scale. The A minor scale has the exact same notes as the C major scale except that in A minor the A note is the root and the most common chord in the key of A minor is A minor. For the A major scale the relative minor is F# minor. The root note(F#) being three frets below the A note, so the minor scale pattern above (blues scale + black dot notes) is also a scale pattern that can be used for playing lines in major key songs, only note 2 would be the root. This is what modes are - The key of A minor is the relative minor mode of the C major scale, it uses the exact same notes but uses a different note as the root and a chord named after this note will be the most common chord played in a song in that mode.
   The Dorian minor mode uses the second note of a major scale as its root. The relative dorian minor mode of the A major scale is B dorian minor. The relative natural minor is F# minor. Each of the minor modes has a distinct sound, The three most common chords in a song in A natural minor are Am, Dm and Em. For A Dorian minor its Am, DMajor and Em.  The song "Evil Ways" by Santana uses Dorian mode, I think its G Dorian minor, so to recap, as dorian mode uses the second note of a major scale as its root, G dorian is a mode of the F major scale.
  There's also a Phrygian Minor mode that uses the 3rd note of a major scale as its root, but it's a bit harder to use,  you have to develop your ear to get a feel for the characteristics of the way it sounds. It's easy to drift out of the mode and end up playing in major scale or one of the easier modes, the licks and lines you play have to sound like they resolve to the mode root note, the mode notes must sound "right". The chord progression you're playing over has to be right for the mode to start with. The mode based on the 4th  and 5th notes are called respectively the lydian and myxolydian modes. "Reeling in the Years" by Steely Dan, uses the G lydian mode, ( a mode of the D major scale) at least in the solos, the chord progression alternates two bars each of a G major chord and an A major chord.  Myxolydian mode is fairly easy to develop a feel for, once again the chord progression you're playing over must be in the mode for it to sound right. The mode based on the seventh note (locrian) of the major scale is not often used, it's really difficult to master I haven't attempted it myself yet, and may never get around to it.


                                     

   When you learn any of this stuff it's important that you understand how to use it, it's not esoteric theory, it has real practical uses in songwriting and playing situations. It's possible with lots of practice and playing experience to put any of the twelve chromatic tones into a solo, and do it in a manner that doesn't sound like playing wrong notes, though with some styles of music, this might be inappropriate, i.e. in Country music for instance, solos are generally confined to only the scale notes.
   If you can't find or don't know a song that uses a certain mode - come up with a chord sequence yourself that does, learn by playing along with that. That's the way I did it. My songs "Rising Tide" and "Damn Your Eyes" use myxolydian mode, "Streets of the City" uses Dorian mode,  "Coulda Shoulda Woulda" uses Phrygian mode. "Hearts of Darkness" and "These Blues", are based on the natural(Aeolian mode) minor scale. "Around About Midnight"  uses both the natural minor plus another scale called the Harmonic Minor Scale. Also, when I wanted to learn to play over music that had key changes I wrote songs that did. "Opportunity" in particular, in the verse has an eight bar chord progression that changes key every bar.

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