Music technology can provide persons who experience physical and/or intellectual barriers using traditional musical instruments with a unique access to active music making. This applies particularly but not exclusively to the so-called group of people with physical and/or mental disabilities. This paper presents two Accessible Digital Musical Instruments (ADMIs) that were specifically designed for the students of a Special Educational Needs (SEN) school with a focus on intellectual disabilities. With SnoeSky, we present an ADMI in the form of an interactive starry sky that integrates into the Snoezel-Room. Here, users can 'play' with 'melodic constellations' using a flashlight. SonicDive is an interactive installation that enables users to explore a complex water soundscape through their movement inside a ball pool. The underlying goal of both ADMIs was the promotion of self-efficacy experiences while stimulating the users' relaxation and activation. This paper reports on the design process involving the users and their environment. In addition, it describes some details of the technical implementaion of the ADMIs as well as first indices for their effectiveness.