Band in a box real tracks is what you really need. Try sampling a few utube videos or go to the PG site.
To my ears MIDI is never satisfactory. Rest assured that with real tracks you will be able to create authentic bluegrass, or at least country style tracks in a variety of genres all in less than a minute (once you know how to neter chords). Thats the great thing about BIAB it may be quirky, but it gets you playing immediately.
The demos are easy for YOU to create

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