This root first appeared in The Etymologies of the 1930s as ᴹ√NYEL “ring, sing, give out a sweet sound”, with derivatives like ᴹQ. nyelle/N. nell “bell”, ᴹQ. nyello “singer” and N. nella- “sound (of bells)” (Ety/NYEL, EtyAC/NYEL), though an earlier hint of it might be seen in the Gnomish verb G. nelu- “ring (tr. & intr.)” from the Gnomish Lexicon of the 1910s (GL/60). Tolkien also mentioned this root in the first version of Tengwesta Qenderinwa from the 1930s (TQ1) as having a variant √NYOL, also meaning “ring” but representing a deeper sound (PE18/45).
In the second version of Tengwesta Qenderinwa from the early 1930s (TQ2), he gave the variants as √ŊYEL/√ŊYOL “ring”, in keeping with his decision to remove initial palatalized dentals from Primitive Elvish. A similar set of variants √(Ñ)GYEL/√(Ñ)GYOL “ringing” appeared in a list of sound roots from around 1959-60 (PE17/138).
Neo-Eldarin: For purposes of Neo-Eldarin, I think it is best to ignore Tolkien’s decision to remove initial palatalized dentals from Primitive Elvish, and I recommend retaining √NYEL as the root for “bell” words.
The unglossed root ᴱ√SALA appeared in the Qenya Lexicon of the 1910s with derivatives like ᴱQ. salma “lyre, small harp” and ᴱQ. salumbe “harping, music” (QL/81). The root √SAL appeared again Common Eldarin: Verb Structure from the early 1950s to illustrate the reformed perfect form of its verb Q. asálie (PE22/132), but since these later forms are unglossed it is unclear whether they have the same meaning (“✱harp(ing)”) as the earlier version of the root.