At first glance, jazz theory may appear to be complex and overwhelming. Thankfully it doesn’t need to be that way once it is broken down. The most common building block is a chord progression known as the two-five-one progression (ii V I). The numbers relate the chord’s position in relation to a specific key center (the "I" chord).

Most, if not all, jazz standards contain or are written around the ii V I progression. That is why it is important to learn these progressions in all major and minor keys. The song "Autumn Leaves" is solely based on this progression using major and minor variations in one key. "All the Things You Are" is an example of one song that uses the progression in numerous keys.

The basic chords include the 1^st, 3^rd, 5^th, and 7^th scale degrees. As you learn more about chords you can substitute the 5^th and 1^st degrees with upper extensions such as 9^ths and 13^ths. In the following examples I have added a few of these extensions.

Figure 1 shows the progression in the key of C Major.

Figure 1. ii V I in C major (root on 5^th string)

Figure 2 shows the progression in G Major. It contains the same basic chord types, but with the root (1^st degree) of the I chord on the 6^th string instead of the 5^th. Eventually you will learn to voice the chords in several inversions to suit the particular passage.

Figure 2. ii V I in G major (root on 6^th string)

Figures 3 and 4 show the progression in a minor key. In this case we are in f minor (relative to A flat Major with four flats). The key signature now makes the ii chord what is called half diminished (gm7 with a flatted 5^th degree). Any extensions that are added to the V chord must obey the key signature. For example: The 9^th degree of a C chord would normally be a D natural. Since the key of A flat major/F minor has a D flat, the note added to the C chord is a D flat or a flat 9.

Figure 3. ii V I in F minor (root on 6^th string)

Figure 4 places the root on a different string. In this scenario the note added to the V chord is the 13^th, which normally would be an A natural. As before, the key signature indicates that any "A" will be flat, the note is now a flatted 13. This chord could also be written as a C7 augmented (sharp 5).

Figure 4. ii V I in F minor (root on 5^th string)

The last of the basic chords is a fully diminished seventh chord (figure 7). It can be used in many situations as a passing chord. For example in B flat "Rhythm Changes" (figure 5), you can substitute the Gm7 with a B diminished seventh chord in the first measure (figure 6).

Figure 5. Standard Rhythm Changes (first two measures)

Figure 6. Rhythm Changes With Dim7th (first two measures)

Figure 7. Diminished Seventh Chords

These chords I have presented are simply a place to start playing jazz. All of these chords are barre chords and can be moved up and down the neck. Now get out your fake book and start reading through some tunes. I would recommend starting with something simple such as "Autumn Leaves" "All The Things You Are" or "I’ve Got Rhythm".