Just to thread creep this a little.
Have any other catters published any eBooks, music or otherwise?

I have done my Anglo concertina tutor and have now done a pictoral record of a collection of model aircraft. In both cases it has been a way to produce a document that is quite a niche topic and where a physical copy might not be the best way to proceed.

I suppose that this is another parallel creative process, in the way that many of the musically creative seem to have other creative interests.

Robin