You are purchasing the written music arrangement of "Oh, Danny Boy" arranged for string quartet (violin 1, violin 2, viola, cello).  This can also be used with a vocal soloist.  It is in the key of C with a range of "A" below middle C to "E" a tenth above middle C.  This is a beautiful simple reflective arrangement very appropriate for weddings, funerals or other services.  Be sure to listen to the mp3 audio of the arrangement and check out the score sample.  This is relatively easy to play.  Check out other arrangements at www.hansencharts.com  Email us if you have any questions, need a key change or piano part at harkup@gmail.com.  Thanks and enjoy.