Yes, the MIDJAY can do the job.
But to be fair, the MIDJAY does more jobs than just the arranger keyboard duty. It also has a built in hard drive and can record and play back .wav or mp3 files, also can mix them with the MIDI at the same time in the real.
It also can change pitch and speed of wav files with very little artifacts heard and the vocal eliminator is there, too, to remove most of the lead vocal from a prerecorded track, karaoke style.
But if all you want or need is the autoaccompaniment, it may be overkill for that task -- or maybe not.
There are some softwares that can function as autoaccompaniment keyboards do via MIDI, a google search should bring up candidates, search for "autoaccompaniment software" and then sort out the ones that work from keyboard vs the ones that work via hand entered chords (Band in a Box, Jammer, etc.).
--Mac
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"Keep listening. Never become so self-important that you can't listen to other players. Live cleanly....Do right....You can improve as a player by improving as a person. It's a duty we owe to ourselves." --John Coltrane
"You don't know what you like, you like what you know. In order to know what you like, you have to know everything." --Branford Marsalis