Final answer:
Yes, the sentence is a compound-complex sentence.
Step-by-step explanation:
A compound-complex sentence contains two or more main clauses and one or more subordinate clauses. In the given sentence, 'The drummer feels contrite' and 'instead of forgiving him they begin on an escape plan' are the two main clauses. 'But' is the coordinating conjunction that joins these two clauses. 'Although the drummer feels contrite' is the subordinate clause that begins with the subordinating word 'although'. So, yes, the sentence 'The drummer feels contrite, but instead of forgiving him they begin on an escape plan' is a compound-complex sentence.