If you miss the old option on Tumblr that lets you filter search results by post type, this greasemonkey script is a good fix. You need Firefox and Greasemonkey for it to work.
O, happy day!! This has been driving me crazy.
Except.. I can’t seem to get anything filtered. Confused.
Aha!!! Figured it out. Click the magnifying glass next to the search box. Set your parameters (mydashboard/audio, Tumblr/everything, myposts/photos, etc). Then add a term into the search box itself, or if you don’t want to search by term, just click inside the search box and hit enter. Voila!