It would need to be defended in court yeah, but the absence of that defence doesn't automatically make it so it falls under the GPL and can be included in MIT licensed code just because the copyright holder doesn't know about it to defend it or refuse to be part of your software. Maybe you can argue the technicality but certainly not in the spirit of open source. There would be hundreds of other breakbeats you could include and give away under your MIT license if that were the case.

Pretty sure that aggressive defense is required for trademarks and not copyright. However it may be interesting whether or not it's still protected by copyright.