The victims were shot inside the building on West 37th Street around 12:13 a.m. Tuesday.
Authorities say 34-year-old Kamir King, of Harlem, was shot in the head in the third floor space.
A second unidentified man was shot in the torso and discovered on West 37th Street. A gun was found under his body.
Both men were pronounced dead at Bellevue Hospital.
Police responded to a report of shots fired in the building during what was described by witnesses as a recording session in the commercial space.
They were preliminarily looking for a group of possibly three suspects who fled the scene.
The group appears to have entered the space and gotten into a dispute with King, who performed under the name Haarlem Starr, and members of his group before shooting him.
Friends of King were unable to identify the second dead man, and his connection was unclear.
The motive also remained unclear, but sources said the suspects who showed up at the recording studio came to settle a beef and that it was not a robbery.
“We all have to protect ourselves and be careful in places like recording studios with random people meeting up,” friend George Mims said.
Mims, who goes by GMims and is also an artist, had known King for years. Both graduated from Frederick Douglass Academy in Harlem.
“He was a really dope rapper, dope producer,” he said. “Part of the nucleus in my school of artists.”
GMims said he was looking forward to working with King.
“A mutual friend of ours had hit us up, was talking about doing some music,” he said. “So it’s very likely he was working towards something in that direction.”
Ex-Brit turned Manhattan resident since 2008.