I am certainly not a Trademark Attorney (or any kind of lawyer), but I was under the impression that, regardless of the registration of a Trademark, ignoring its enforcement is the same as giving it up. Hence, by you posting here that your band leader didn't care about the other band infringing on his Trademark, the Trademark can be fought in court and declared abandoned or something similar.
Again, not an attorney, just passing along some information that I thought might be accurate and worth looking into.
See page 22 of this document from the Patent and Trademark office.
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Throughout the life of the registration, you must police and enforce your rights. While the USPTO
will prevent another pending application for a similar mark used on related goods or in connection
with related services from proceeding to registration based on a finding of likelihood of confusion,
the USPTO will not engage in any separate policing or enforcement activities.