first string (of a shamisen, etc.)
Refers specifically to the thinnest, highest-pitched string on a shamisen or similar traditional Japanese instrument. The term is used in musical contexts.
The first string of the shamisen broke, so I replaced it with a new one.
Formed from 一 “first” and 糸 “string.” On the shamisen, 一の糸 is conventionally the lowest-pitched and thickest of the three strings.