Knight of Ghosts and Shadows(1990)
(The first book in the Bedlam's Bard series)
A novel by Ellen Guon and Mercedes Lackey
Eric Banyon, musician, is out playing the blues on his flute one day, but he couldn't have known that the desperate sadness of his music would free a young elven noble from the magical prison he has been languishing in for centuries--nor does he believe it!
Used availability for Mercedes R Lackey's Knight of Ghosts and Shadows
June 1990 : USA Mass Market Paperback