MPD_sima is a non interactive MPD autoqueue client running in the background. It will queue new tracks chosen among artists similar to your current queued tracks, provided a title is found in your music library.
Default is to fetch similar artists from last.fm webservice. There are other plugins to fetch tracks based on genre tag or using specific complex filter.
Depending on the plugin used, MPD_sima can queue track, top track or whole album for similar artists.
This client allows you to never run out of music when your queue is getting short.