Immediately chose the correct value!
The trick lies in listening to the reverb of the instruments and voices in the music.
In general this style of music is easy to compress, due to few high frequencies, and quality is very even, but there are plenty of songs that will give you artificial noise in the higher frequencies.
My recommendation to you would be to have all encoded in OGG.
The average songs don’t compress as well as this one did (did you compress in 128kbit avg, or variable bitrate, or did you encode it …

OK, these guys are completey crazy.  Taken from their website:
The Vegetable Orchestra performs on instruments made of fresh vegetables.
The utilization of various ever refined vegetable instruments creates a musically and aesthetically unique sound universe. The Vegetable Orchestra was founded in 1998. It consists of 11 musicians,