What does 'his patience a sympathetic string' mean?
Brief introduction of the content:
Anahita, the wife, kept complaining her son's missing last night. Arshan, the husband, were searching in ditches last night, fearing his son was crashed by any cars or trucks alike.
What does "his patience a sympathetic string' mean" in the following paragraphs:
‘And while you were at this Steiner School nightclub,’ Anahita interrupted,
raising her hand, ‘free as a bird, your father was in the ditches!’
‘No,’ Arshan said, his patience a sympathetic string. ‘I’m pretty sure
the ditches came later, sweetheart. So, what happened at the club, that
put you in jail?’