Regular chords become altered chords when the 5th, 9th or 11th note is altered. Some of the names can be confusing but it's really pretty simple.
An easy way to remember the 9th is that a flatted 9th is one note higher than the root of the chord. A raised 9th also a minor 3rd(same note) is 3 notes higher than the root.
These chords can be major, minor or dominant chords like G7♭5. A 9th chord always has a 7th in it, don't confuse this with the “add 9” you may see on some chords.
Some of our symmetrical and modal scales can be used for improvising over these chords.
The only notes that can be altered are the 5th, 9th and the 11th
The 2 and the 9 are the same note one octave apart, the same for the 4 and 11. The 2 and 4 don't get altered but they can act as the 9 or 11 in some chord configurations where the 9 or 11 are too far away to be used in a practical chord form. The 6 and the 13 are the same too but these notes can't be altered, only 5, 9 and 11. The 5th can be lowered 1/2 tone or raised 1/2 tone or both can be in the same chord. The 9th can be lowered or raised 1/2 tone and can be combined with an altered 5th or 11th. The 11th can only be raised 1/2 tone, It can't be lowered because it would become a major 3rd. Also the 11 and 4 are the same note one octave apart. This note gives that suspended 4th sound that wants to resolve. A raised 11th is also a lowered 5th note one octave apart. Remember in chord building theory for guitar octaves don't count except for our ears. Any octave will have the same effect on the chord. The magic number for finding the same notes is 7. Add 7 to 2 you get a 9, subtract 7 from 9 you get a 2. This works for all the other numbers.
The 2 and the 9 are the same note one octave apart, the same for the 4 and 11.
The 2 and 4 don't get altered but they can act as the 9 or 11 in some chord configurations where the 9 or 11 are too far away to be used in a practical chord form.
The 6 and the 13 are the same too but these notes can't be altered, only 5, 9 and 11.
The 5th can be lowered 1/2 tone or raised 1/2 tone or both can be in the same chord.
The 9th can be lowered or raised 1/2 tone and can be combined with an altered 5th or 11th.
The 11th can only be raised 1/2 tone, It can't be lowered because it would become a major 3rd.
Also the 11 and 4 are the same note one octave apart. This note gives that suspended 4th sound that wants to resolve.
A raised 11th is also a lowered 5th note one octave apart.
Remember in chord building theory for guitar octaves don't count except for our ears. Any octave will have the same effect on the chord.
The magic number for finding the same notes is 7. Add 7 to 2 you get a 9, subtract 7 from 9 you get a 2. This works for all the other numbers.
If you need help understanding chords and scales these pages will help.
The 5th of a chord can be lowered or raised.
A C chord C-E-G would become a C flat 5 C-E-G♭
A C chord C-E-G would become a C aug C -E-G♯
Notice that a chord that says aug or augmented after its letter name always refers to the 5th of the chord unless a number comes after the aug or augmented.
Other symbols used are the plus (+) sign(C+5) and the sharp (♯) sign(C♯5) for augmented or raised notes.
Don't confuse the add with the + sign. The add means to add a note(C add 9) not raise it a half tone like the + sign.
The minus sign(-) is used sometimes for flatted notes(C7-5). It makes the chord symbol shorter and easier to fit in written music.
In the second C♭5 above you have to arch your first finger slightly so the 4 and 2 strings are muted.
The 7th chord is a dominant chord built from the 5th note of the major scale.
Don't confuse this with a major 7th chord, this 7th is 1/2 step higher.
In the key of C the chord would be a G. The dominant chords start with the 7th chord.
The first chord is a G. G-B-D.
The next chord is a G7. G-B-D-F.
The next chord is a G9 G-B-D-F-A.
The 7th can have one or more of the following alterations.
A flat 5, sharp 5 or both.
A flat 9, sharp 9.
A sharp 11 which is equal to a flat 5.
Unless you play Jazz you most likely won't run into the 11th or 13th alterations.
However understanding this process will help your understanding of chord symbols in other areas.
The only song I can think of that uses the flat 5 so you will recognize it is Led Zepplins' Dancing Days written by Jimmy Page and Robert Plant.
This isn't a true flat 5 because there is no 3rd until the last beat.
You go back and forth on the first two chords, actually notes and end on the last.
You will have to use some palm muting so the chords ring out the right length of time.
Here are links to the mp3 and sheet music.
An augmented chord usually but not always comes after an unaltered form of the same chord. When used like this it is leading you into another chord usually with a note in it 1/2 tone higher than the raised 5th.
Here is a common progression you will see in a lot of songs.
See how the 5th of the C chord moves up 1/2 tone at a time.
See how the name of the chords change.
The A minor could be called a C6 although there would be no 5th in it.
The C7 would most likely lead to some form of an F chord.
The Beatles song Oh Darling starts with an augmented chord.
The flatted 9th chords will be written as a 7th chord like C7-9 or C7♭9.
You can think of the flatted 9th note as a raised root. This note will always be 1/2 tone above the root note of the chord it in.
These chords are the beginning of The Beatles song I Want You(She's So Heavy) from the Abbey Road Album
All the picking is on the 1st 4 strings, no 5th string notes even though they are in the chord.
Here is a link to the CD because you can't download individual Beatles songs in mp3.
This chord is a popular altered chord. I've heard this refered to as the Jimi Hendrix chord.
He uses this chord in Stone Free.
It can also be used with the flat 9 as a substitute chord sequence like E7+9, E7-9 to E7. this is good if you have a couple of bars of E7 in a row to spice it up.
P.S. Don't get in the way of the melody or a solo. Play around until you can make it fit or wait for another song if it doesn't work on the current one.
What makes this chord really unique is that a sharp 9 is also a flat 3 or a minor 3rd.
This means you can use minor scales and major scales freely for improvising with this chord.
You can use the E Mixolydian, E major and minor pentatonic, the E major and minor blues scales, the E Super Locrian mode, the F diminished scale and more.
The F Diminished isn't an error, it's sometimes easier to think 1/2 step above with this scale to get the notes for altered chords in the scale. This scale contains the major 3rd and the minor 3rd/augmented 9th.
Here are links to the mp3 and sheet music for this song.
This is the only alteration for this note. If it was lowered it would equal a major third which isn't an altered tone.
What the difference between this and a 7th flat 5 chord is that it has a 9 in it.
I don't know of a popular song that has this chord in it that you would recognize offhand.
If I come across one I'll put it up but this chord has a unique sound to it. Here are a couple diagrams.
These are dominant chords putting you in the key of A. E is the 5th and dominant note of the A scale.
The T for the fingering means thumb. Wrap your thumb over the neck to play these two notes on strings 5 and 6.
The 2nd chord image has no root, follow it by the 3rd on the 4th string. think E-3 ='s C.
When we get a lot of notes in a chord we leave out tone to play the ones that are wanted. The bass player will play the root or it will sound implied. In other words the listener thinks they hear the root it because of what was played before this chord. You have already set the stage.
These chords could be used to replace a C7 for a couple of beats to spice up the progression.
There is no root for the 2nd and 3rd chords so you must remember them in a different way.
The 2nd chord has its 3rd on the 2nd string. Think back two whole tones to C.
The 2nd chord has its 3rd on the 3rd string. Think back two whole tones to C.
E will always be the 3rd of any C major, augmented or dominant chord.
This is one way. You might choose one of the other notes to reference by but I find the 3rd a good way because it doesn't ever change unless a chord doesn't have one.
Like the chords above the 2nd and 3rd image have no root.
Sometimes a chord diagram will tell you no root with a NR after the chord name. Most of the time they don't unless it's a lesson.
The 3rd for the 2nd image is on the 4th string. Think E-3 ='s C
The 3rd for the 3rd image is on the 2nd string.
I told you about chords that have a sharp and flat 5 in the same chord here are a couple examples.
This chord may also be called a C7♭5♭13 because a sharp 5 is equal to a flatted 13 which is equal to a 6th but one octave higher.
There are more but these are the most common.
You don't have to play Jazz to take advantage of this theory. The individual notes from these chords can be used in improvising in any style of music if played at the right time and tempo.
I hope you found this page useful.