non-strawberry solution: if your playlists are in a central location (e.g. /Music/playlists/) then you could 'search within files / search file contents' using whatever OS-default search tool you have handy?
Now if you were feeling INCREDIBLY saucy, you could setup a cron job to
scan all your playlists create a database of songs [track URL] (rows) & playlists (columns), with cells filled by the playlist name; have a final column which concatenates all nonblank playlist columns, separated by semicolon Write that final column to the Performer tag of those files [manually/auto rescan collection in Strawberry then) search "performer:MyPlaylist" if you want the contents of the playlist in whichever Collection grouping scheme you've chosen (potentially useful/interesting), or (your main objective) search for the song and look in the tags for the performer, or display the performer tag as a column.
