John Gill Commentary Genesis 4:21

"And his brother`s name was Jubal: he was the father of all such as handle the harp and pipe." — Genesis 4:21 (ASV)

And his brother's name was Jubal
This was another son of Lamech by Adah, and his name differs only in one letter from his brother's;

he was the father of all such that handle the harp and organ :
he was the inventor of instrumental music, both of stringed instruments, such as were touched by the fingers, or struck with a quill, as the "harp"; and of wind instruments, such as were blown, as the "organ", which seems not to be the same we call so, being a late invention; but however a pleasant instrument, as its name signifies. Jubal is thought by some to be the same with Apollo, to whom with the Greeks the invention of the harp is ascribed; and some have been of opinion, that the jubilee trumpet was so called from Jubal, (Leviticus 25:9) . Sanchoniatho

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FOOTNOTES:

• F18: makes Chrysor or Vulcan, the same with Tubalcain, the brother of Jubal, to exercise himself in eloquence, songs and divination, confounding or mistaking the employment of the two brothers. The Arabs have such a notion of the Cainites being the inventors of music, that they commonly call a singing girl "Cainah" ^F19 ; and the Arabic writers
  F20 make Jubal to be the first inventor of music, and that the beasts and birds gathered together to hear him; the same that is said of Orpheus.