Keane was Dyche's final signing of the summer transfer window.
He told the club's website: "Michael is a young up-and-coming player who he is a good addition to our squad.
"He has enjoyed good development through various loan spells over the past year or so and we felt that he could enhance the group.
"It was a late one because there were a few twists and turns to the situation and it took a bit of work but sometimes with the ins and outs, especially the ins at Manchester United, meant they had a lot of work to do."
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