To find music put "kind:audio" or "kind:music" in the search field (no quotes). For video, use "kind:movie". For a size limitation, hit Apple-F or select "find" from the file menu or start typing anything in the search bar (even a single space) and then click on the plus that appears immediately below it. Then in the rows of options that appear immediately below the search bar, select "size" as the criteria, the appropriate "greater" or "less" and the appropriate size. You can also specify kinds using the "kind" criteria in the same place you select the "size" criteria. Use the "+" if you want more options.