A pedal tone is a note that persists while the harmony changes. Sometimes, the pedal tone is not part of the harmony. Pedal tones over the tonic or dominant are common. In the following example, Bach establishes a dominant pedal tone. In the fifth measure, however, we find a chord unrelated to the G pedal tone: (F# - A - C - Eb):

We find pedal tones in the middle and higher voices. In this passage, Beethoven uses a B as a pedal tone in the middle voice: