Another way the major scale pattern can be used is for the quick calculation of chord progressions and transposing songs into different keys. Each key has its own diatonic chords that are found by harmonizing it's major scale. The resulting chords from this process will always form the same specific pattern:

The primary chords found in the key of Amaj, for example, would therefore be:

and can be extended to:

and further to:

This pattern remains the same for any key. The intervals shown before the chord names can be identified by using the major scale pattern we already know. To work out what chords are in the key of Bb, you would place the major scale pattern at the 6th fret, count off the 7 intervals as you play them, and relate the chord names to them in the correct sequence. This would give:

Each chord can be referred to as it's location in the key followed by it's chord type for convenience (i.e., the II chord, the V chord or the I chord), as the basic harmonic structure will always be the same. If the chord has been extended or substituted, this should be specified i.e., V9 chord or IVmaj9. You will often hear other musicians refer to chord progressions as I, IV, V or II, V, I. These are common terms and tell you the type of progression being used regardless of the key. All you would need to know is what key you are playing in to be able to play the progression with no problems.

This is in fact the way most professional players communicate in jamming situations and is also the way to transpose songs from one key to another (an inevitable task should singers be involved). To do this, you must first identify a chord progression in terms of its key. The easiest way to do this is to look at the sheet music, if available, and identify the key signature. If this is not possible, try to identify which chord is the dominant chord and work backwards. You can look at the minor chords to double check your answer. If all else fails, just ask someone!

Once the key has been identified, the next step is to assign the chords in the song their function within the key. Convert all chords to the form described above (Amin7 may become a IImin7 in the key of Gmaj). Once all the chord names have been assigned, it is a relatively simple task to transpose them to the new key using the major scale pattern to work out the new chords in the new key.