I have a metal clarinet. They have been popular as band instruments over the years. The British Army and a lot of American bands used them in the early 20th century; there's usually one for sale on eBay at any time (generally a B flat Boehm-system). Mine is a Turkish Albert-system clarinet in G, which was introduced in France as the "clarinette d'amour", rendered in Turkish as "ashk klarneti" which is closer to"lust clarinet". It's a handy size for Scottish music, as in the low register it fingers like a D whistle and in the upper register like a pipe chanter in A. At the low end I either play an improvised alto line or else do fiddle tunes an octave down.

A friend of mine has a double-walled E flat metal clarinet. The double-wall construction (like a thermos with tone holes) was a late 19th century attempt at making a metal clarinet that sounded like wood. Since it was a lot more expensive to make than a wooden model it didn't really take off.

Play enough woodwind instruments and distinctions between their techniques more or less evaporate. You alter the pitch of a note by partial opening, cross-fingering or providing an extra hole. That's not a lot of alternatives to remember. Mentally you organize them rather like object-oriented programming: think of fingering systems as falling into hierarchical subgroupings. If you've got a key you use it, if you haven't you crossfinger, if that doesn't work you half-hole.

The one that really doesn't fit is closed fingerings for bagpipes like the Border pipes, where (more or less) only one hole is left open. With other instruments you think about what fingers you're putting down, with these you think about the fingers you're *not* putting down. Still boggles my mind a bit.

I'd still like to know what the original poster's tune is.