Sorry, Forum censor was having a field day with some of the topics we were discussing. I must have been half-asleep to not realise I was reading moderated posts.

Keep in mind the network is reliant upon what people share. So if nobody is sharing a particular topic then obviously you won't find it. As previously mentioned, sometimes it is worth trying certain unsuccessful searches at varying points of the day (if possible.)

Music:

Try different searches in this order:
artist, album title (unless it's brief), portion of song title (unless it's brief.)

I originally preferred doing an All Types search & then simply filtered it by audio. Else of course you can use the Audio type search. One issue is a percentage of files shared do not have ID3 tags to help with searches, only the file-name gives the clue which is why an All Types search can sometimes bring in a few extra results.

If the artist is a band, sometimes it can be worth doing a gnutella search for the name of the most popular member of the band.