Stone Song, the third book in the Cold Iron series is out June 9. Here, D.L. McDermott offers an inside look at how the book came to be.

When I started the third book in my Cold Iron series, Stone Song, I knew I wanted my heroine to be an Irish folk musician who my hero, Elada, the loyal right hand man of Fae sorcerer Miach MacCecht, has admired from afar for a long time. And I knew I wanted them to meet at Boston’s Black Rose, a bar near Faneuil Hall with a lively traditional music scene.

That was the easy part. The tough part was that I wanted to give Sorcha powers that stemmed from her musician abilities, and I wanted her to be able to channel those powers through an instrument that could also be a weapon. When I started researching traditional Irish music, I discovered the perfect thing in Ireland’s wire-strung harp, the cláirseach.

The cláirseach is the triangular harp you see on Irish coins and that appears in the Irish coat of arms. When I discovered that the metals used to string this harp included not only brass but gold, silver—and most importantly for fighting the Fae—iron, I knew I’d found Sorcha Kavanaugh’s weapon.

In Stone Song, Sorcha has traveled the globe learning how to play the wire-strung harp, but it’s only when she encounters the Fae that she learns the instrument’s true power—and her own Druid gifts.