a.k.a. Yal, or Yarl
Yazh is a harp. Although it is extinct, it is found carved into the walls of temples, and still plays a part in the cultural self identification of Tamil Nadu.
The spelling and pronunciation of yazh is somewhat problematic. “Zh” is a sound which is found in Tamil, Marathi, Sanskrit, and a number of other Indian languages. It would be closes to an “rl” therefore “yazh” is often transliterated as “yal” or “yarl”. Probably the best English transliteration would be “yaarl”.
There are numerous references to the yazh in Tamil literature. It is mentioned in the poetic work Perumpanarruppatai (circa 1st century), the Silappatikaram (circa 5th century), and the Tirukkuraḷ (circa 3rd century). As late as the 20th century, a very extensive work about this instrument was written by Swami Vipulananda entitled Yazh Nool. It is also commonly displayed in temple bas relief in places such as Darasuram and Thirumeyyam in Tamil Nadu, or Amaravathi in Andhra Pradesh.
The yazh was not a single instrument but a class of instruments of the harp family. Literary references describe the various forms of yazh in some detail. The sagoda yazh (14 stringed), makara yazh (19 stringed), senkottu yazh (7 stringed) are mentioned. Additionally they could be described as vil yazh (bow shaped), or mayil yazh (the form of a peacock).
It is often said that the modern Saraswati veena evolved from the yazh. But the morphological differences between the two instruments, coupled with an absence of any intermediate forms, makes this a highly unlikely. This view is more likely to be a mere reflection of traditional Hindu world views than the actual evolutionary path.