an Anglo concertina which had a three-row keyboard and was thus chromatic

For melody, sure - but even on a three-row Anglo I bet there are plenty of chords that you can't get at all, and chord sequences that you can't realistically play (e.g. eight bars with four successive 'push' chords).

Thanks for reviving this thread, Dick - I'll look out for your book, once I've got a box to learn on.