premise: a man with beard sitting down playing an acoustic guitar. hypothesis: The band sets up their instruments.
contradiction: A band is a group while a man is a single person, also while the man is playing an acoustic guitar, the band sets up their instruments.|contradiction: He refers to a man, not a band. Also, a guitar is one instrument so you can't pluralize a single instrument.|contradiction: A man sitting down playing acoustic guitar is singular and specific, while band sets up their instrument is plural  and vague.