Unspecified fictional instrument used in the bombastic symphony (opus 8421) by composer/conductor Horridnoise, in the far flung future of 1995, from the satirical review "The Symphony in 1995," published in 1885, in music magazine The Etude, November 1885 (Volume 03, Number 11).
It's so big, a special giant balloon is being built specifically to carry it to the moon, so Horridnoise can perform his symphony there. So it must be an integral part of this symphony.
So it must be a massive, mechanical wind instrument of some kind, based on the "cornet" and "whistle" parts of it's name. The "ether" part is intriguing, as that was the then-theorized mysterious medium that filled outer space and allowed light to propagate. So perhaps this device can propagate sound through the aether, or uses it to produce sound instead of air. Or, uh, both?
...we give below a detailed description to our readers in the world, and also for the benefit of those of our subscribers in the moon who have been unable to visit us this season, owing to the exorbitant rates. We are happy to inform the latter that Horridnoise proposes to treat them to a performance of his work, as soon as the large balloon necessary to carry the enormous instrument (the cornetetherwhistle) is finished.