Yamaha psr sx700 replaces the psr s770 / psr s775.
see an explanation of voice and style types on the yamaha psr sx700 below
yamaha psr sx700 keyboard features
986 voices, including 131 super articulation voices and 24 organ flutes. 41 drum/sfx kits
400 styles, including 353 pro styles, 34 session styles, 10 dj styles and 3 free play
pre-installed expansion content
400mb on-board memory for expansion data
1gb internal memory
midi song file capacity : 3mb per file
joystick, fsb keyboard for powerful live performance
intuitive and fast control with 7" color touch screen and assignable function
mic/guitar input for use when singing or collaborating with other performers
audio recording (wav/mp3)
voice and style expandability with the yamaha expansion manager
main differences between psr sx700 and psr sx900
986 voices vs 1337(psr sx900)
131 super articulation voices vs 952 (psr sx900)
400 styles vs 525 (psr sx900)
400mb on-board memory vs 1g (psr sx900)