I already play the piano to a pretty high level, but was really interested in learning more about the field of piano tuning etc as hopefully a holiday job…
I would assume that it is impossible to learn from another piano tuner since they would hardly want to create more competition, so an online course seemed like the most likely alternative – or maybe there is a book or better way to go about this?
Actually, apprenticeship is still the preferred route. Many of the active tuners/technicians are older and would like to slow down or retire. A rebuilding shop may have several workers, and could be an ideal place to get a start. There have also been many who have left the field leaving too much work for others. The hard part is being in a market where there are still a lot of acoustic pianos. Often cities or affluent areas of larger towns. So many pianos have been replaced by digitals.
Anyway, the only online/in home tuning course that consistently gets high praises is Randy Potter’s http://www.pianotuning.com/
One more thing. If you go this route, do join the piano technicians guild. http://www.ptg.org/ and live up to the standards of a true tuner. Anyone can buy a tuning hammer and mutes and run around calling himself a piano tuner, but having the credentials gives you opportunities with professional organizations who may need tuning. Restaurants, orchestras, night clubs, etc.
Also three books for the bookshelf: The pierce piano atlas: http://pianoatlas.com Larry Fine’s Piano book; http://www.pianobook.com/ and Arthur A. Reblitz’ "Piano Servicing, Tuning, and Rebuilding": http://www.amazon.com/Piano-Servicing-Tuning-Rebuilding-Second/dp/1879511037 (Maybe also "Pianos and Their Makers by Alfred Dolge – though it’s an older book)
… And if you’re in New England, there is no better program than the North Bennett Street School in Boston: http://www.nbss.org/programs/piano-technology/index.aspx