(Reuters) -Hipgnosis Songs Fund (HSF), which holds the rights to the work of artists ranging from Shakira to Neil Young, said on Tuesday its investment adviser has refused to drop a call option that is complicating its bid to sell off some of its music. The adviser, Hipgnosis Songs Management (HSM), is run by the fund’s founder Merck Mercuriadis and backed by private equity firm Blackstone. The call option gives it the right to purchase the fund’s music portfolio if and when its agreement with the fund is terminated. HSF has said the option is a “structural conflict between the interests of ou…