You need to create a form, and add a combo box.
In your query, you need to add the parameter
[Forms!].[Formname].Value (or something similar, I can't remember of the top of my head).
Set the combobox up to have values from another query, which produces the list cds, records, tapes.
Then add a button to your form, which runs the report, which should be basedon the original query.
I hope that makes sense, if not, post back again.