with metal keys. Since the modern revival of the recorder, plastics have been used in the mass manufacture of recorders, as well as by a few individual makers. Today, a wide variety of hardwoods are used to make recorder bodies. Relatively fewer varieties of wood are used to make recorder blocks, which are often made of red cedar, chosen because of its rot resistance, ability to absorb water, and low expansion when wet. A recent innovation is the use of synthetic ceramics in the manufacture of recorder blocks. Larger recorders Some recorders have tone holes too far apart for a player's hands to reach, or too large to cover with the pads of the fingers. In either case, more ergonomically placed keys can be used to cover the tone holes. Keys also allow the design of longer instruments with larger tone holes. Keys are most common in recorders larger than the alto. Instruments larger than the tenor need at least one key so the player can cover all eight holes. Keys are sometimes also used on smaller recorders to allow for comfortable hand stretch, and acoustically improved hole placement and size. When playing a larger recorder, a player may not be able to simultaneously reach the keys or tone holes with the fingers and reach the windway with the mouth. In this case, a bocal may be used to allow the player to blow into the recorder while maintaining a comfortable hand position. Alternatively, some recorders have a bent bore that positions the windway closer to the keys or finger holes so the player can comfortably reach both. Instruments with a single bend are known as "knick" or bent-neck recorders. Modern developments Some newer designs of recorder are now being produced. Recorders with a square cross-section may be produced more cheaply and in larger sizes than comparable recorders manufactured by turning. Another area is the development of instruments with a greater dynamic range and more powerful bottom notes. These modern designs make it easier to be heard in concertos. Finally, recorders with a downward extension of a semitone are becoming available; such instruments can play a full three octaves in tune. German fingering In the early twentieth century, Peter Harlan developed a recorder with apparently simpler fingering, called German fingering. A recorder designed for German fingering has a hole five that is smaller than hole four, whereas baroque and neo-baroque