It is not permissible to sell musical instruments, since they have no value according to Shari`ah (Islamic law) and their price is ill-gained because it is paid in return for a prohibited object. Allah (Glorified and Exalted be He) says,
And whosoever fears Allâh and keeps his duty to Him, He will make a way for him to get out (from every difficulty).
And He will provide him from (sources) he never could imagine.
May Allah ease things for you!
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.