The 'perfect voice.' Synonymous with the term 'single voice.' （一音） The voice of the buddha. Various explanations are: （1） All the teachings （Maha^ya^na， Hi^naya^na， etc.） are all really forms of one teaching; （2） the single perfect teaching is understood differently by listeners of different capacity; （3） the Huayan 华严 understanding of the 'single voice' which automatically adapts to the capacity of the listener.