I just remembered my aunt and uncle near Enniskillen used to have an instrument that sounds just like those described by Greg B. I had forgotten about the chord buttons, but i do remember they had some sort of fan. Can't say if they were mains-powered or battery (the one they had was fairly small). Hardly more than a kid's toy, it was nevertheless capable of producing a pleasant sound. I guess it had brass or possibly steel reeds, nice mellow sound, in tune with itself at least, and I think the fan/blower noise wasn't too obtrusive. I used to play it on visits there in the early '70s. Was really disappointed to find they had traded it in when upgrading to a Hammond organ!

Around the same time, I had a Hohner Melodica (I haven't seen it for years, but it may still be around). I think Hohner produced an adaptor to provide a powered wind-supply (or maybe I'm thinking of somebody's home-made effort?) Wouldn't have quite the same street-cred as a harmonium down the folk-club, but could be a cheap way of finding out if you like singing to the accompaniment of reeds!

Ross