How about one of these...

http://larkinthemorning.com/product.aspx?p=HOR563

Looks like a miniature trumpet. If it works the same way, it could be very loud, but you'd need a little practice to make it work, and you'd have to be healthy enough to yell to use it. If you were a musician and your "chops" were in good shape, you could blow it for hours at a time, but if not, you'd be limited to short bursts. (Used to play trombone in a former life.)

Now I'm wondering if I'd stand out if I took an old trombone out as a survival signal.

In my experience, the musical instrument that carries the farthest is bagpipes. However, this would be a bad choice for a rescue signal, as nobody would ever walk toward them.

Hunting horns are easy to blow and they travel well, its not so common these days but you used to be able to go into the English countryside and hear hunting horns all over the place.

Any modern (read: tough plastic) versions of these? I'd carry one.

Release the hounds!

Not that i am aware of, they are a very traditional horn for the hunting set.

I like the sound af a air horn thay make
a smaller one that wold fit nice in a small backpack.but thay are not very realiable.

litlefoot01
you don't multiply wealth by dividing it.

I've been thinking about getting a SuperHorn Air Horn.

Does anybody know what makes bagpipes so loud?
All they really are is a set of reeded flutes. maybe there is a way to make something as loud but much smaller or something as loud out of improvised parts.

It's the angry Scotsman attached to them.

(Kidding, I'm kidding.)

I know a guy who has a chanter (the flute piece that the notes are played on) and they're not that loud. Though they still grate, which is why East Coast rock-and-rollers work them into their songs.

So there must be a resonance thing involved somewhere in the whole octopus. I can't imagine that the kilt has any effect, no matter how much lanolin is rubbed into it.

bike horn?..the ones with the rubber bulb..you could honk out a SOS..