Ages 3-12. Below age 3, most children's hands are too small to play the piano, the fingers cannot bend or move independently, and the brain and body (vocal chords, muscles, etc.) may not yet be sufficiently developed to deal with concepts in music. Above age 4, most children are able to receive some type of music education, especially if they have been exposed to music since birth; thus they should be constantly tested for their sense of pitch (relative and perfect pitch; can they "carry a tune?"), rhythm, loud-soft, fast-slow, and reading music, which is easier than any alphabet. This group can take full advantage of the enormous brain growth that takes place during this age interval; learning is effortless and limited more by the ability of the parents to provide the appropriate practice schedule than by the student's ability to absorb music. One remarkable aspect of this age group (there are many!) is their "malleability"; their "talents" can be molded. Thus, even if they would not have become musicians if left alone, they can be made into musicians by proper training. This is the ideal age group for starting piano. Mental play is nothing special – it comes naturally to this age group. Many adults consider mental play a rare skill because, like perfect pitch, they lost it during their teen ages from a lack of use. Therefore, make sure that they are conducting mental play, playing music in their minds.
Ages 13-19, the "teen" ages. This group still has an excellent chance of becoming concert level pianists. However, they may have lost the chance to become those super stars that the younger beginners can become. Although brain development has slowed down, the body is still growing rapidly until about age 16, and at a slower rate thereafter. The most important factors here are the love of music and the piano. This age group can achieve practically anything they want to, as long as they have an intense interest in music. However, they are not malleable any more; encouraging them to learn piano does not work if they are more interested in cello or saxophone, and the parents' role changes from giving direction to giving support for whatever the teens want to do. This is the age interval in which the teens learn what it means to take responsibility and what it means to become an adult -- all lessons that can be learned from the piano experience. In order to influence them, you need to use more advanced methods, such as logic, knowledge, and psychology. They will probably never forget anything they memorized at these ages or younger. Above this age group, age classifications become difficult because there is so much variation among individuals.
Ages 20-35. Some individuals in this age group still have a chance of becoming concert level pianists. They can use the experience they learned in life to acquire piano skills more efficiently than younger students. Those who decide to learn piano in this age group generally have greater motivation and a clearer understanding of what they want. But they will have to work very hard, because progress will come only after a sufficient amount of work. At this age group, nervousness can start to become a major problem for some. Although younger students can become nervous, nervousness seems to increase with age. This happens because severe nervousness arises from fear of failure, and fear arises from mental associations with memories of terrible events, whether imagined or real. These terrifying memories/ideas tend to accumulate with age. Therefore, if you want to perform, you should do some research into controlling nervousness, by becoming more confident, or by practicing public performance at every opportunity, etc. Nervousness can arise from both the conscious and subconscious brain; therefore, you will need to deal with both in order to learn to control it. For those who just want to become sufficiently technically proficient to enjoy playing major piano compositions, starting in this age group should not present any problems. Although some maintenance will be required, you can keep anything you memorized in this age group, for life.
Ages 35-45. This age group cannot develop into concert level pianists, but can still perform adequately for simpler material such as easy classics and cocktail music (fake books, jazz). They can acquire enough skill to play most famous compositions for personal enjoyment and informal performances. The most demanding material will probably be out of reach. Nervousness reaches a maximum somewhere between the ages of 40 and 60 and then often declines slowly. This might explain why many famous pianists stopped performing somewhere in this age interval. Memorizing starts to become a problem in the sense that, although it is possible to memorize practically anything, you will tend to forget it, almost completely, if not properly maintained. Reading the music can start to become a problem for some who require strong corrective lenses. This is because the distance from the eyes to the keyboard or music stand is intermediate between reading and distant vision. Thus you may want a set of eye glasses for intermediate vision. Progressive lenses might solve this problem, but some find them bothersome because of their small field of focus.
Ages 45-65. This is the age range in which, depending on the person, there will be increasing limitations on what you can learn to play. You can probably get up to the level of the Beethoven Sonatas, although the most difficult ones will be a huge challenge that will take many years to learn. Acquiring a sufficiently large repertoire will be difficult, and at any time, you will be able to perform only a few pieces. But for personal enjoyment, there is still a limitless number of compositions that you can play. Because there are more wonderful compositions to learn than you have time to learn them, you may not necessarily feel a limit to what you can play. There is still no major problems in learning new pieces, but they will require constant maintenance if you want to keep them in your repertoire. This will greatly limit your playable repertoire, because as you learn new pieces, you will completely forget the old ones, unless you had learned them at much younger ages. In addition, your learning rate will definitely start to slow down. By re-memorizing and re-forgetting several times, you can still memorize a significant amount of material. It is best to concentrate on a few pieces and learn to play them well. There is little time for beginner's books and exercises – these are not harmful, but you should start learning pieces you want to play within a few months after starting lessons.
Ages 65+. There is no reason why you can't start learning piano at any age. Those who start at these ages are realistic about what they can learn to play and generally do not have unattainable expectations. There are plenty of simple but wonderful music to play and the joy of playing remains just as high as at younger ages. As long as you are alive and not terribly handicapped, you can learn piano and make satisfactory progress at any age. Memorizing a composition you are practicing is not a problem for most. The greatest difficulty in memorizing will come from the fact that it will take you a long time to get up to speed for difficult material, and memorizing slow play is the most difficult memory work. Therefore, if you choose easy pieces that can be brought up to speed quickly, you will memorize those more quickly. Stretching the hands to reach wide chords or arpeggios, and fast runs will become more difficult, and relaxation will also be more difficult. If you concentrate on one composition at a time, you can always have one or two compositions that can be performed. There is no reason to modify your practice methods -- they are the same as those used for the youngsters. And you may not feel as much nervousness as you might have in the middle ages. Learning piano, especially memory work, is one of the best exercises for the brain; therefore, serious efforts at learning piano should delay the aging process, just as proper physical exercise is necessary to maintain health. Don't get a teacher that treats you like a young beginner and give you only exercises and drills – you don't have time for that. Start playing music right away.