Much of Sun Ra's music could be classified as free jazz, especially his work from the 1960s, although Sun Ra said repeatedly that his music was written and boasted that what he wrote sounded more free than what "the freedom boys" played. "The Heliocentric Worlds of Sun Ra" (1965) was steeped in what could be referred to as a new black mysticism. But Sun Ra's penchant for nonconformity aside, he was along with Coleman and Taylor an integral voice to the formation of new jazz styles during the 1960s. As evidenced by his compositions on the 1956 record "Sounds of Joy", Sun Ra's early work employed a typical bop style. But he soon foreshadowed the free jazz movements with compositions like "A Call for All Demons" off of the 1955–57 record "Angels and Demons at Play", which combines atonal improvisation with Latin-inspired mambo percussion. His period of fully realized free jazz experimentation began in 1965, with the release of "The Heliocentric Worlds of Sun Ra" and "The Magic City." These records placed a musical emphasis on timbre and texture over meter and harmony, employing a wide variety of electronic instruments and innovative percussion instruments, including the electric celeste, Hammond B-3, bass marimba, harp, and timpani. As result, Sun Ra proved to be one of the first jazz musicians to explore electronic instrumentation, as well as displaying an interest in timbral possibilities through his use of progressive and unconventional instrumentation in his compositions.