(32) Arpeggio, Cartwheel Motion, Finger Splits
Playing arpeggios (arps) is technically complex. Arps are "broken chords"; notes of "chords" played in succession. Arps are complex because many (36) Hand Motions, such as flat finger positions, thrust, pull, cartwheel motion (below), glissando, finger splits (below), TU or TO, must be combined. Those trained to use only curled finger positions will find arps to be scary difficult. Because of the large distances between notes, it is difficult to hit every note accurately.
Arps are played TO just like scales. TO arps is an extreme example of TO and serves as a clearer example of TO than for scales. TO is more necessary for arps than for scales because the thumb cannot be tucked under the hand to reach the next position — the distance is too far. New motions are needed to cover these longer distances accurately.
The standard arp fingering for the CEGCEG . . . .C arp is 123123. . . .5, RH, and 5421421. . . .1, LH ascending, and the reverse for descending. See Michael Aaron, Adult Piano Course, Book Two for fingerings of all arps and scales. Because arps jump over several notes, most people spread the fingers to reach those notes. For fast arps, this is a mistake because spreading the fingers slows down their motions and builds stress and fatigue. A better method is to move the hand instead of spreading the fingers, using the cartwheel motion and finger splits.
The cartwheel motion is especially useful for small hands. Place the left palm flat on the piano keys, with the fingers spread out like the spokes of a wheel. The fingertips from pinky to thumb fall on an approximate semi-circle. Now place the pinky above C3 and parallel to it; the hand must be rotated so that the thumb is closer to you. Then move the hand towards the fallboard so that the pinky touches the fallboard; the hand must be spread out at all times. If the 4th finger is too long and touches the fallboard first, rotate the hand sufficiently so that the pinky touches the fallboard, but keep the pinky as parallel to C3 as possible. Now rotate the hand like a wheel counter clockwise (viewed from above) so that each successive finger touches the fallboard (without slipping) until you reach the thumb. This is the cartwheeling motion in the horizontal plane. A supple wrist is needed for this motion.
If your reach is one octave, the cartwheeling motion should cover almost two octaves! Extra reach is gained because the center three fingers are longer than the pinky or thumb, and the circumference of a semi-circle is larger than its diameter.
Now repeat with the hand vertical, so the fingers point down. Start with the pinky vertical and lower the hand to play C3. Then roll the hand up towards C4; each finger will "play" the note that it touches. When you reach the thumb, this motion should cover almost twice the normal reach. We just learned three things: (1) how to "cartwheel" the hand, (2) this motion expands the reach without making any jumps, and (3) the motion can be used to "play" the keys without moving the fingers.
Cartwheeling is used with the hand somewhere between vertical and horizontal, and the fingers will be in the pyramid position [(4) Curled and Flat Finger Positions, Curl Paralysis] or slightly curled. Although cartwheeling will add keydrop motion, the fingers should also be moved to play the notes. Cartwheeling in the horizontal plane uses only the slow sideways motion of the wrist. Cartwheeling in the vertical plane uses the much faster motions of forearm rotation.
Your reach can be stretched even more by using "finger splits" (Fraser). Make a "V"with fingers 2 & 3 of the RH and place the "V" on a flat surface, at the edge, so that only the two fingers are on the surface and the rest of the hand is off the edge. Spread the "V" as far as you can, comfortably. Then rotate the arm and hand 90 degrees clockwise (supinate) so the fingers are now touching the surface with their sides. Now it is possible to spread the fingers even more; this is called finger splits. This works with any pair of fingers. Cartwheeling expands the reach to almost twice normal; adding finger splits expands it to over twice normal. Demonstrate this by repeating the above cartwheel motion, but with added finger splits.
The flat finger positions [(4) Curled and Flat Finger Positions, Curl Paralysis] are the best for playing arps because they allow play with the large front pads of the fingers. This greatly reduces the chances of missing those narrow black keys. Those who use curled fingers on black keys find arps scary and frustratingly difficult.
Therefore, by using a combination of TO, flat finger positions, cartwheel motion and finger splits, you can easily reach and play fast arps with little stress on the stretching muscles. This complex combination of motions is facilitated by a supple wrist and forearm rotation. As with every complex technical motion, practice each of the above individual motions separately before combining them.