Other horns
I made both of these horns from recycled materials. They are both brass instruments, as they are played with a trumpet mouthpiece. They work on the principle of finding the critical length relative to the bore of pipe used, this gives all the notes in a diatonic scale. Neither instrument have any holes, valves or sliding tubes to create the different notes, it is all done with lip muscle tension.
The 'crumpled horn' is made from a copper immersion tank heated and beaten into the horn bell shape. The heat exchanger coil from the inside of the same tank then provides spiral copper length. The 'crumpled horn' is in Db (D-flat) with a one octave range and has a mellow sound like french horn.

crumpled-horn-streatham

The 'seahorn'; I found this day glow public address horn, probably from a ferry/cruise ship, at Dorchester metal recycling centre. It is about 1.25 metres long and made of aluminium with about 3.5 metres of 15mm copper tube attached. The range is over 2 octaves of diatonic (normal) scale in the key of Eb. It has a strong sound when a trumpet mouthpiece is used.

.seahorn
2

playing on stage at The Exchange Sturminster Newton