I sing and play with Crucible and we do teach singing workshops at festivals so I'm always interested to hear other people's hints and tips about this sort of stuff.

My own route in to harmony singing was through improvising (vocally and instrumentally) in sessions and, initially, singing in school choirs. Not sure how I learned about improvising harmonies on the fly, it just sort of evolved as I was growing up. We used to sing a lot as a family, in the car and so on. I absolutely love being part of a big group of voices all singing different notes but making a big fat chordal sound. For that reason I really enjoy singing Sacred Harp although I don't get to do it that often.

I didn't really get into arranging close 4 part harmony till after we formed the band and I am constantly fascinated by different approaches even between the 4 of us who perform together. Sometimes we'll improvise and record our improvisations and pick the best of what we'd made up and then (usually) write it down, sometimes we'll arrange more theoretically on paper making chords between the available voices. Most often its a mixture of those two approaches. Often the creative bit is only coming from 1 or 2 of the band with the others then being given a part to learn, but it's not always the same 2. Two of us out of the four in the band are comfortably musically literate but the other two aren't and using the two approaches gives a big mixture of everybody's input. Not to say that it always works- we've abandoned songs in the past because we just couldn't find a set of harmonies that we liked or were all comfortable with.