As suggested by David Salo (GS/§4.180), the phonetic developments of the primitive aspirate [pʰ] as well as the spirantal sounds that developed from [b] were most likely bilabial spirants [ɸ] and [β] to begin with, developing into labio-dental [f] and [v] later. The occasional appearance of ꝑ and ƀ for these sounds in Tolkien’s writing supports this idea, such as on PE22/28 and PE19/101. One indication that this change was relatively early is the example: phelgai > felʒi > fili (NM/304); this example indicates the labial became a bilabial before i-affection, but it must be taken with a grain of salt, since Tolkien simply have been representing labial [ɸ] with f. Most likely this sound change occurred at all conceptual stages of Tolkien’s languages.