We are going to Spain the end of April and I just wanted and audio guided tour of the Monastery. I've tried the website but having a hard time finding information on how to book.
I’ve booked a guided tour for Monserrat in May so I’m not able to answer your specific question. However on the web page for Monserrat there is a “contact us” area where you can submit your question. When you enter the site you’ll be faced with a Covid update. You are in the correct area. Simply scroll down to the input box.
https://www.montserrat-tourist-guide.com/en/general/contact-us.html
That's NOT the official site, that's the link of a private company. Montserrat's website is https://www.montserratvisita.com/en/index.html Not saying anything against intermediaries, just pointing it out, for clarity purposes.
The link above is not presented as the official site for Monserrat but rather as a potential site to provide an answer for the question being asked. It is also not the site from which I purchased tickets.