Because as usual I was in my experimental mood, I asked her to play a soprano and sing the alto which she did. She seemed surprised since I asked her to do it without any warning. But she gladly played the excerpt this way. Then she would play all the combinations of 2 voices always singing one and playing the other.
Then she knew what was coming up next - to play all the combinations of 3 voices always singing one and playing the remaining two. It wasn't easy. She struggled a little but did it nonetheless.
And finally there came a time to play all 4 parts together and sing one. Since she practiced all the previous steps, now it wasn't something out of reach. She completed the exercise almost successfully.
The reason I asked her to do all of these acrobatics was not only that I wanted to show her how to hear individual voices as clearly as possible but I also wanted to test her.
I wanted to test how far she could go without saying, "No, that's enough". In fact in the middle of the exercise I explicitly told her that it would be OK to quit this and play as usual. She never once told me to stop doing my experiments on her. This obviously wasn't the end of her limits of curiosity.
I think our organ playing in public is a lot like this too.
We are not playing the organ in recitals or church services simply to let our audience and ourselves to feel good. Well, yes, we do, but we also secretly hope to push the limits just a little bit.
Not too far that we may lose the connection but just enough to make them uncomfortable and be OK in their discomfort.
I'm not saying such state is easy to achieve.
Push a bit too far and your listener may never trust you again. Relax the musical reins too much and the entire experience will not be too different from a pop concert.
It's a really thin ice.
[HT to Egle]
Practice I-V6-I-IV6-I64-V-I (G major) in four parts. See example.