Avestan Yye and a Distinction of Position

Two signs for one glide is a distinction of position rather than of sound, and it is the kind of detail that only survives in a tradition copied with care. The manuscripts observe it consistently enough that editors reproduce it. A script made in the Sasanian period for a text composed a thousand years and more earlier is an act of preservation rather than of composition. Nothing was being written down for the first time. What was being done was the fixing, in a form that would not drift, of something priests already held in memory. The script was put to a second use as well.

Pazand is Middle Persian written in Avestan letters, taken up precisely because those letters record vowels and the Pahlavi ones did not, and it is the clearest practical demonstration of what the alphabet was good for. In the digital record the letter is encoded at U+10B2A AVESTAN LETTER YYE. The whole Avestan block lies above the Basic Multilingual Plane, so each character needs a surrogate pair in the encodings that use them, and a font carrying the script is required before anything appears on a screen at all. The practical test of the alphabet is whether a reciter reading from it produces what the tradition received, and by that test the fineness of its distinctions is not ornament. Each of the signs that looks redundant from outside answers to something a reciter kept apart.