The pedal point (or "stuck key")

We haven't talked much about alternate bass notes for chords. Normally the bass note is the same as the chord's root note, but you can specify a different bass when you find a musical need for it.

The bass note follows a slash after the chord name. For example, C/E indicates a C major chord with the note E in the bass.

Any note, whether it's a member of the chord or not, can be specified as an alternate bass note. In theory this opens up a huge range of possibilities -- every single chord has the potential for 11 alternate versions -- but, in practice, alternate bass notes in rock songs are limited to a few conventional formulas.

One of these formulas involves keeping the bass on the same note while the chords move around. This tends to reduce or offset any sense of motion that the chords are creating. Here are a few simple examples:

||: C G/C F/C C :||
||: C Dm/C Em/C F/C :||

Most often, the bass stays fixed in the early part of the verse, so that when the bass later starts moving around freely, the sense of motion is amplified.

The traditional name for this technique is pedal point, and the name refers to the pedals of pipe organs that play the lowest bass notes. An organist could plant one foot on one of the bass notes, while playing moving chords with both hands. (Some adventurous synthesizer players use MIDI versions of these organ pedals, because two hands aren't always enough.)

You could also think of this the "stuck key" technique, because it's as though a synthesizer key has gotten stuck in the down position, so it persists in playing the same note while the rest of the music keeps moving.