I couldn't agree more with Matthew than if I'd been sitting in the organ loft myself. I speak as one who wears his collar back-to-front but who is also a wannabe organist. If you're going to to play something special at the end of the service, and you've taken care to choose a voluntary that fits with the Gospel - just as we have chosen and spoken on a theme that fits the Gospel - then we appreciate your work and will support you. We clergy may seem to be the worst offenders, in some ways, because we generally stand at the back and say the dismissal prayers, then perforce talk to the members of the congregation who wouldn't listen to the organ if you stuck one of the front rank up their nose for a good sniff.
If I'm honest, I'd rather listen to what you're doing with the best of all musical instruments than I would listen to the story of how Mrs Unguent's leg has been playing her up this week or about how Fluffy the pet pirrhana has developed a distressing rash - but the celebration of the Sacred Mysteries seems to bring out volubility in the congregation, and who am I, a servant of the Church (with a capital "C") to deny them the chance to relate such stories? If I could clamp them all to their pews for the duration of the Toccata in G, I would; but I can't, and that's the way the world is - However, I do occasionally hear myself saying to a parishioner ""hang on a minute, I love this bit..."
Though we may be your worst enemies in some cases, bear in mind that most of us in the clergy were brought up with ecclesiastical music, and may actually be the ones who most want to listen to your playing. I admit, there is no accounting for some clerical eedjit who wants to replace the glorious instrument that was installed in a church to replace the gallery band, by introducing a CD player or some gratingly-bad set of guitarists and a tambourine player, but there are those in every sphere of life who will make change for change's sake.
Incidentally, somebody asked "what do you do about an overly-loud Vicar?" Well, many of you sit in an elevated position and, especially in the grander Gothic buildings, no-one would see you aiming the hunting rifle with the fitted silencer...
Oh, and about Theo's comment about educating us poor clerics... Some of us do try to maintain a degree of solemnity about what's just been sung or played; mind you, I speak as a member of what might be called the "Cartholick" tradition, where it's usual to maintain a period of silence - and what would you, as organists, do about a player who assumes that the cleric has gone to sleep, or forgotten what's happening, so (for example) starts playing the Nunc before there's been a suitable pause after the second lesson ar Evensong? Or the one who insists on playing Appleford's appalling two-tone siren noise for "Christ has died" before us chaps up the front have finished reverencing the Sacrament at the second elevation?