Apparently from reading around, MewSeek just uses a few search engines to get its music. If you find out these websites, i suppose you can always just open them in the browser and download as you like.

For the time being, you can use google. Just change music title to the song name artist etc (and add + where the space is supposed to be) eg:
http://www.google.com.au/search?hl=en&q=music+title+intitle%3A%22index.of%22+%28mp3|aac%29+-htm+-html+-asp+-php+-listen77+-airmp3+-shexy+-vmp3+-hyooge+-audiozen+-musicindexof+-mp3s+-musik+-eucontest&aq=f&aqi=&aql=&oq=&gs_rfai=