One of the most common chord types is the seventh chord, (sometimes called the dominant seventh chord). The seventh chord consists of four notes taken from the major scale of the same letter name. These notes are the first (1), third (3), fifth (5) and flattened seventh (b7) notes of the major scale, so the chord formula for the seventh chord is:
A flattened seventh (b7) is created by lowering the seventh note of the major scale by one semitone. Notice that the seventh chord is simply a major chord with a flattened seventh note added. The C7 arpeggio with inversions is shown here.
Here is a bass line which makes use of a C7 arpeggio. Once again, remember that as long as you play the correct notes for any arpeggio, these notes can be arranged in any order.