Open voicing, also called spread voicing, is a style of musical arranging or orchestration in which the notes of chords are assigned across a range wider than one octave. The lowest note of an open voicing is almost always the root of the chord; occasionally it may be the fifth. Here's a simple example of open voicing: Start with a C major triad middle C (C3), E, and G. Now move the C down one octave (to C2). Next lower the G one octave, to G2. Leave the E where it is and add a high C (C4). C2 - G2 - E3 - C4 is the resulting open-voiced chord, spanning two octaves. In big band arranging, chords voiced in this manner were often called "pads", and were used in much the way we now use synth pads.