いとみち

いとみち【糸道】

〔糸爪〕 an indentation [a groove] that develops in the fingernail of the left index finger of a samisen player from friction with the strings; 〔三味線[琴]の演奏技能〕 《a player's》 samisen [koto] playing ability.

●糸道があいている can play a samisen respectably [decently, competently].