Late sixties advert for the Leslie 900, highlighting some of the innovative features of this amplifier.
MORE POWER. The Leslie model 900 is equipped with an amplification system more than twice as powerful as any of the standard single-channel Leslie speakers. GREATER VERSATILITY. A single channel input is divided into three independent channels of amplification, each with its own speaker system. The treble and bass are electronically separated to achieve greater clarity and strength. The reverb has a unique Leslie tremolo generator that adds just the right amount of warmth, while retaining a bigness of sound and depth of tone. For combo instruments there's versatility another way, too. With a pre-amp it can simultaneously handle two single channel organs, or one guitar and one organ, or two guitars or any other amplified musical instrument.