I have been reading The dark legacy of shannara series by Terry Brooks and a couple of characters possess the power of the Wishsong. It seems a rather powerful power to possess, but I am only provided examples of its capabilities in this series. Is there a book or series he has written which explains the Wishsong in more detail. I don't wish to read all his books (at least not at this time) but i am quite interested in understanding more about this magic.

I have been reading "The Dark Legacy of Shannara" series by Terry Brooks and a couple of characters possess the power of the Wishsong. It seems a rather powerful power to possess, but I am only provided examples of its capabilities in this series. 

Is there a book or series he has written which explains the Wishsong in more detail? I don't wish to read all his books (at least not at this time) but I am quite interested in understanding more about this magic.