You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Queen_(band)

Context:
After working on various solo projects during 1988 (including Mercury's collaboration with Montserrat Caballé, Barcelona), the band released The Miracle in 1989. The album continued the direction of A Kind of Magic, using a pop-rock sound mixed with a few heavy numbers. It spawned the European hits "I Want It All", "Breakthru", "The Invisible Man", "Scandal", and "The Miracle". The Miracle also began a change in direction of Queen's songwriting philosophy. Since the band's beginning, nearly all songs had been written by and credited to a single member, with other members adding minimally. With The Miracle, the band's songwriting became more collaborative, and they vowed to credit the final product only to Queen as a group.

Question:
Who did Freddie Mercury collaborate with in 1988?

Montserrat Caballé, Barcelona