Patricia C. Wrede 
Harp of Imach Thyssel [PDF ebook] 

In the magical world of Lyra, a mysterious instrument gives a minstrel undreamed-of power When Emereck and Flindaran leave a caravan in search of adventure, it isn’t long before they stumble upon great danger. Emereck, a trained minstrel, and Flindaran, a nobleman masquerading as a tramp, have found a long-abandoned castle, and in it, one of Lyra’s most sought-after treasures: the Harp of Imach Thyssel.Emereck recognizes the perfect white bow from legend: It is said to possess the power of life and death over all mankind. Now, to keep it from falling into the wrong hands, he’ll have to learn to harness its strength to create and destroy, with the fate of the kingdom hanging in the balance.