white keys. The first pedal keyboards only had three or four notes. Eventually, organ designers augmented this range by using eight notes, an approach now called a "short octave" keyboard, because it does not include accidental notes such as C, D, F, G, and A. The 17th-century north German organ builder Arp Schnitger used an F and G in the lowest octave of the manuals and pedal keyboards, but not a C and D. From the 16th to 18th centuries, short octave keyboards were also used in the lowest octave of upper manual keyboards. By the 14th century, organ designers were building separate windchests for the pedal division, to supply the pipes with the large amount of wind that bass notes need to speak. These windchests were often built into tall structures called "organ towers". Until the 15th century, most pedal keyboards only triggered the existing Hauptwerk pipes already used by the upper manual keyboards. Beginning in the 15th century, some organ designers began giving pedal keyboards their own set of pipes and stops. In the 15th and 16th centuries, the pedal division usually consisted of a few 8′ ranks and a single 16′ rank. By the early 17th century, pedal divisions became more complex, with a richer variety of pipes and tones. Nevertheless, the pedal division was usually inconsistent from one country to another. 17th century to 18th century By the beginning of the 17th century, organ designers began to give pedalboards on large organs a larger range, encompassing twenty-eight to thirty notes. As well, German organ designers began to use longer, narrower pedals, with a wider space between the pedals. By this point, most pedals were given a smoother lever-action by including a fulcrum at the back of each pedal. These design changes allowed performers to play more complex, fast-moving pedal lines. This gave rise to the dramatic pedal solos found in German organ works from composers from the North German organ school, such as Dieterich Buxtehude, Johann Adam Reincken and J.S. Bach. In Bach's organ music the cantus firmus melody, which is usually a hymn tune, is often performed in the pedal, using a reed stop to make it stand out. Several sources, including an encyclopedia on the organ, claim that the pedalboard design improvements of the 17th century allowed the organist to actuate the pedals either with the toe of the foot or with the heel.