Music education is an important part of the school curriculum; it teaches children to be creative and to collaborate with others. Music gives individuals another medium to communicate through, which is especially important for individuals with cognitive or physical disabilities. Teachers of children with severe disabilities have expressed a lack of musical instruments adapted for these children, which leads to an incomplete music education for this group. This study aims at designing and evaluating a set of collaborative musical instruments for children with cognitive and physical disabilities, and the research is done together with the special education school Rullen in Stockholm, Sweden. The process was divided into three main parts; a pre-study, building and designing, and finally a user study. Based on findings from previous research, together with input received from teachers at Rullen during the pre-study, the resulting design consists of four musical instruments that are connected to a central hub. The results show that the instruments functioned as intended and that the design makes musical learning accessible in a way traditional instruments do not, as well as creates a good basis for a collaborative musical experience. However, fully evaluating the effect of playing together requires more time for the children to get comfortable with the instruments and also for the experiment leaders to test different setups to optimize the conditions for a good interplay.