Some of the reviews on tripadvisor are pretty dire on the whole for that hotel.
The prices they charge £340 per night for the cheapest room threadbare towels and €11 for a beer + €20 for a Pizza which took them approx 1 Hour to serve Lol would not be me staying there.
It also said Traffic noise on the 5th floor was really bad.
So looks like the sound proofing is not up to much, maybe people standing outside will be able hear the concert.
There is a hydralic service elevator straight in to the Gran Saló Gaudí for their eqipment but I expect security will be tight.
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www.tripadvisor.co.uk]