sentences:  While simultaneously sounding the open D string, he also added a droning quality reminiscent of the sitar's sympathetic strings.Music writer Alan diPerna describes Beck's playing as a milestone and helped introduce "the psychedelic subgenre known as 'raga rock'", which became popular during 1966 and 1967.William Echard adds "'Heart Full of Soul,' released in June 1965, is often said to have marked the arrival of raga rock [and] be pivotal in shaping the look and sound of 1960s psychedelia."