With the dramatically improving fidelity of electric sound recording in the 1920s, aural spatiality - traces of room ambience and reverberation - became a factor in record production. Drawing on prior radio broadcast practice, a split occurred whereby 'fine' orchestral musics were recorded with relatively high levels of ambient or atmospheric sound while dance music, popular songs, humorous recitations and other 'low' forms were generally recorded with little or no reverberation. Through the 1930s and 1940s, popular recording occasionally, though increasingly, made use of mechanically fabricated echo and reverb to present a kind of sonic pictorialism, especially on singing cowboy and popular 'Hawaiian' recordings. Hollywood film sound practice in this period employed similar sonic space-making devices to denote states of terror, mystical revelation and supernatural transformations. The coming of rock 'n' roll in the 1950s, with its characteristic big echo and reverb production sounds, may be seen as the radical recombining of these contradictory antecedents, effected in such a way as to allow (and promote) disordered, non-pictorial sound spatialities.