Harpist Úna Ní Fhlannagáin explains why the sound of a harp string is not easily read by an electronic tuner, or tuning app.
Here's the description (referenced in the video) of how overtones and harmonics occur:
https://music.stackexchange.com/quest...
Here's a companion tutorial on how to improve the performance of your tuner / tuning app, and make your harp tuning easier: • Video
www.una.ie
Úna performs a range of Irish dance music, Celtic music, and Celtic songs, with occasional explorations of folk music outside the Celtic world.