By Swami Harshananda
Sometimes transliterated as: Gandharva-veda, GAndharva-veda, Gaandharva-veda
As Science of music
Veda means science of knowledge. The gandharvas are a class of demigods who were considered experts in the field of music, the science of music including musicology. Hence it came to be known as Gāndharva-veda.
As Literature
Sometimes a work called Gāndharva Veda, comprising of 30,000 verses, is believed to have existed as an Upaveda of Sāmaveda. But it is not available now.
References
The Concise Encyclopedia of Hinduism, Swami Harshananda, Ram Krishna Math, Bangalore
Read & Download "Gandharva Veda" Original Sanskrit Texts:
Sangeeta Ratnakara (Original Sanskrit Text)