Enharmonics.
You may be wondering why harpists always talk about this concept.
For most instruments, ‘enharmonics’ are redundant. Yes, E# the same as F. On the piano, it is exactly the same key!
However, on the harp, enharmonics provide a way to work around some of the inherent limitations.
In this post, we will discuss practical uses for enharmonics, including repeated notes and pedal solutions.
But first, what is an enharmonic? Enharmonic is defined as: Relating to notes that are the same in pitch (in modern tuning) though bearing different names (e.g., F sharp and G flat or B and C flat). (Oxford Languages)
On the harp, enharmonic notes are played on different strings. A C is always played on the C string, whether it is flat, natural, or sharp. A D is always played on the D string, whether it is flat, natural, or sharp. Hence, even though a C# and Db are “enharmonic”, they are still played on separate strings. This means that the pedal positions will be different, the finger patterns may be different, etc.
However, remember that because the harp is diatonic (the unchanged strings spell a major scale), not every note has an enharmonic equivalent.
Enharmonics as repeated notes: On the harp, repeated notes (i.e. the same string) are only possible at a slower tempo. Since each string must be placed in advance before playing, rapid repeated notes are impractical at best. (See posts under #fourmotionsofplaying)
However, if the repeated pitches use two different strings, it can be incredibly idiomatic, even at a trill speed.
(Note: the two strings will have a slightly different timbral sound and the effect is very similar to a timbral trill on wind instruments)
Parish-Alvars La Mandoline, Op. 84 is an excellent example of this technique.