Will God hold me accountable if I let my sisters play music, based on the desire of my father who prevents me from intervening and threatens to expel me from the house if I delete it?

You must advise your family gently and kindly, abandoning threats and warnings. If you enjoin good and forbid evil with wisdom, you have fulfilled your duty, and the disobedience of those who disobey will not harm you thereafter. Remember the great right your father has over you.

As for the oath that your father prevented you from fulfilling, you must offer expiation for it: either freeing a slave, or feeding ten needy persons, or clothing them. And for he who finds not, then a fast of three days.