Here's a link to reviews for the QY-700 if anyone is interested.. It seems to have auto accomp capabilites.. Not sure if they mean auto accomp as it pertains to arranger though..

http://www.harmony-central.com/Synth/Data/Yamaha/QY-700-01.html
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GEAR: Yamaha MOXF-6, Casio MZX-500, Roland Juno-Di, M-Audio Venom, Roland RS-70, Yamaha PSR S700, M-Audio Axiom Pro-61 (Midi Controller). SOFTWARE: Mixcraft-7, PowerTracks Pro Audio 2013, Beat Thang Virtual, Dimension Le.