Traditionally, a "Tetrachord" is a series of four tones filling in the interval of a perfect fourth. In modern usage a tetrachord is any four-note segment of a scale or tone row including the augmented fourth (+4). The term tetrachord derives from ancient Greek music theory, it literally means four strings.**

The G Tuning comes in two versions where string four is either tuned to the "D", a major second below string one or low "D" where string four is a perfect fifth below string three. The G tuning with a low D is the same as the thin four strings of a standard tuned guitar.

Introductions are a composed or improvised pieces of music that introduce - sets the stage for - a song or composition. Introductions, or intro for short, are used in all types of music. In this lesson, the focus is on introductions in contemporary pop, rock, blues, country, folk and jazz styles.

An "Enharmonic Equivalent" is where a musical pitch can have different names depending on the context in which it is functioning. An example is G# produces the same pitch as Ab but have different standard notations when written in music.

Alternate fingerings for F7 in C tuning. The same fingerings would apply to C7 in G tuning and G7 in D tuning.