Music Therapy (MT) has shown many benefits in helping autistic children, but some challenges remain due to children's social anxiety and sensory issues. Yet, very few studies have investigated how Virtual Reality (VR) could help to increase the accessibility of MT approaches. This paper presents an exploratory study investigating the use of VR to perform MT sessions for autistic children with severe learning disabilities and complex needs. The study is performed in terms of acceptability, usability, and social communication. A collaborative MT approach was designed in close collaboration with music therapists from Denmark and psychologists from France, using head-mounted display-based VR. Testing were conducted with thirteen children with various neurodevelopmental conditions and intellectual disabilities at a children's day hospital in Paris. The results indicate positive acceptability and usability for these children, and suggest a positive effect of MT in VR regarding communication.