Umlauts resulted in the appearance of the new vowels "y" (like ' from *"fullijaną") and "œ" (like ' from *"dōmijaną"). The umlauts are divided into three categories: "a"-umlaut, "i"-umlaut and "u"-umlaut; the last was still productive in Old Norse. The first, however, appeared very early, and its effect can be seen already around 500, on the Golden Horns of Gallehus. The variation caused by the umlauts was itself no great disruption in the language. It merely introduced new allophones of back vowels if certain vowels were in following syllables. However, the changes brought forth by syncope made the umlaut-vowels a distinctive non-transparent feature of the morphology and phonology, phonemicising what were previously allophones.