G.G., The two sources I have found most helpful advising those who would compose or arrange music for harp, are: (1.)”Harp Scoring” by the late Stanley Chaloupka, who was Principal Harp for 40+ years with Los Angeles Symphony Orchestra in California. Published by himself in 1979 and now widely available from some major harp music dealers. (2.) “The ABC of Harp Playing” by the late Lucille Lawrence, respected harpist and teacher, published by G. Schirmer Inc. New York, 1962 and perhaps updated since then. It is the second half of this book. beginning on page 40, that is mostly valuable for your purposes. You would avoid many, many harp composing errors by becoming well acquainted with the information in these published books. Not to be overlooked is “Writing for the Pedal Harp”, by Inglefield and Neill, that includes a CD of the sounds of various effects unique to harps. Published by U. of California Press, ISBN 0-520 04832-6 in 1985 and surely reprinted since then.