 After 1950 Grainger virtually ceased to compose . His principal creative activity in the last decade of his life was his work with Burnett Cross , a young physics teacher , on free music machines . The first of these was a relatively simple device controlled by an adapted pianola . Next was the " Estey @-@ reed tone @-@ tool " , a form of giant harmonica which , Grainger <unk> informed his stepdaughter Elsie in April 1951 , would be ready to play free music " in a few weeks " . A third machine , the " Cross @-@ Grainger Kangaroo @-@ pouch " , was completed by 1952 . Developments in transistor technology encouraged Grainger and Cross to begin work on a fourth , entirely electronic machine , which was incomplete when Grainger died . 
