I would like to convey a yashar koach to Mitchell First on his recent article about the meaning of “tishkach yemini” (“‘If I Forget You, Jerusalem…’ (Psalms 137:5),” May 30, 2019). An additional point, in favor of an interpretation of a paralysis, or general weakening of the strength (tash koach, one might say) of the right hand: as mentioned in the article, this is an oath form. Specifically, it is an oath starting with a conditional of a bad thing a person does (“If I forget thee”) and a negative result (“let my right hand forget / be forgotten”). A parallel to this could then be found not locally (in the next verse’s tidbak) but in Iyov 31:21-22: “If I have lifted up my hand against the fatherless… Then let my shoulder fall from the shoulder-blade, and mine arm be broken from the bone.” There, it is a more general disabling of the arm, rather than forgetting a particular, musical, skill.
Josh WaxmanTeaneck