I have to agree with friedo. This sounds like an index issue. What kind of indexes do you have on catalog and pivot? If you don't know what I am talking about, then you need to educate yourself on indexes.
Here is how you would create some indexes on these two tables. Enter these in the mysql command line tool.

create index c_atldp on catalog ( author, titulo, label, description, 
+price )

create index a_atldp on author ( author, titulo, label, description, p
+rice )
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You can create several different types of indexes depending on how and what kind of queries you are writing and a full discussion of indexes is OT. Sometimes you need to write new ones for a new type of query.
JamesNC