In June 1867, an English astronomer, meteorologists and an avid balloonist, James Glaisher was floating in the air over Paris in a balloon and he suddenly entered into a region of dense cloud-

        " All on a sudden, when we are suspending in the misty air, we hear a paradisaical concert of instrumental music that seems to come from the cloud itself. It seems it is coming from a distance of a few yards only from us. Our eyes attempt to enter the depths of white, homogeneous, nebulous matter which impale us in every direction. We heard with no little astonishment to the sounds of the mysterious orchestra."

Glaisher had heard such music many times when he fly through clouds. The sound was heavenly.  Five years ago, Glaisher took off in a giant balloon from Wolverhampton city in England. Astonishingly,  he heard a band of music playing that was clear when he was at the height of 12,700 feet.

In 1867, Glaisher, another balloon enthusiasts, Camille Flammarion (a French astronomer), and Gaston Tissandier (a French meteorologist) started a series of experiments with balloon flights. They flew over two days from Paris to Solingen, near Cologne. They heard various sounds several times during this experimental trip, when they were floating above the ground at thousands of feet. “We were serenaded by some excellent orchestral music whilst sailing over Antony and over Boulainvilliers; we were then entirely enveloped by clouds, and about 3,280 feet above each of those towns.”

Glaisher wrote like this on his memoirs of balloon flight, ’Travels in the Air’ :

 " I realize that the intensity of various sounds emitted at the surface of the world is carried up to top heights in the atmosphere. The whistle of a locomotive rises to close 10000 feet, the noise of a railway train to 8,200 feet, the barking of a dog to 5,900 feet; the report of a musket is detected to the same height; the shouting of boys and girls can be heard as high as 5000 feet, and at this altitude the crowing of a cock and therefore the sound of a bell of church are audible. At a height of 4550 feet the roll of a drum and the music of an orchestra are clearly heard. At 3,255 feet in altitude, a man’s voice might build itself heard; the rolling of a cart on the pavement are often distinguished somewhat higher; and within the stillness of the night the course of a stream, or perhaps that of a tiny river, produces at this elevation nearly the result of a high waterfall. At the height of 3000 feet the croaking of frogs can be heard with its intense sound, and the sharp sound of mole-cricket is distinguished simply at an altitude of 2500 feet."

Glaisher and his companions experienced such sounds that were the effect of dense humidity on sound level. It has been experimented that the sound level rises when the humidity of the air  increases. Floating clouds and fog in the sky being more humid “collects sound with such intensity”.  Glaisher also explains that whenever, we were passing through a cloud, we have heard a band playing in a town beneath us, the music always seemed to be close at hand.”

“Generally lower humidity absorbs more sound, especially at higher frequencies, because of "molecular relaxation" in the gases in the air,” explains NPS. The waves of sounds change when they goes through the molecules of the dense fog. All the molecules collect the waves of sound and change it.  “A substantial change in atmospheric pressure, equivalent to thousands of feet of elevation gain, has a small influence on noise level for most sources, but substantially affects the received levels of those sounds.” Glaisher and his companions heard such reactions of the sound above in the sky.