Music is for enjoyment. But, you may argue, music can be for making money, too. Sure, but music does not become valuable as a commodity unless it is somehow enjoyable to someone willing to buy it.

The invention of the automobile includes more than wheels, motor & fuel. The automobile also requires a system of roads. It is fair to say that music was discovered, or simply observed as in the case of song birds. So, we can say that the first musical instrument was, perhaps, the voice. But, music requires more than instruments, it also requires ears.

(Pardon a digression while I get this question out of the way. You may draw your own conclusions. :-)
If a tree falls in the forest and nobody hears it does it make a sound

"Humans perceive sound by the sense of hearing. By sound, we commonly mean the vibrations that travel through air and are audible to people. However, scientists and engineers use a wider definition of sound that includes low and high frequency vibrations in air that cannot be heard by humans, and vibrations that travel through all forms of matter, gases, liquids, solids, and plasmas." (Emphasis added)

According to Wikipedia

If a hit song plays on a radio and nobody hears it, is it still a hit

If an artist plays an original song to a room of 30 people and everyone cheers enthusiastically,
is the song a hit

For every song played on the radio there are hundreds, perhaps thousands, of songs that the music industry does not consider worth investing in (check out Where's the Money.)

"Many developing songwriters resent having to be a businessperson. I've heard them lament, "I've written the songs—now let somebody else take care of the business." But the reality is that this is the music business. The greatest song in the world will not become a hit if it's neither demoed or brought to the attention of music business professionals." (from Learning Where the Money Comes From by Jason Blume)

From the artist's point of view, trying to create and enjoy music while also trying to make a living at it is daunting (check out Making Money....)

"Remember, playing paid gigs and getting a hefty record contract advance are only two ways to make money in this business (although they certainly are great ways to make it). But most musical success wannabes make the mistake of ending their search there." (from Making Money-Making Secrets by Bob Baker)