Mystery Theme ("Phone Tag") by ShapiroA

Question 12

The most prominent Scrabble sets in which a certain letter appears are Icelandic Scrabble, where it is worth 2 points, and Gretchen McCulloch's English IPA Scrabble, in which it is worth 10. The name of that letter is also a playable word in English Scrabble, worth a total of 6 points (or 7 for a variant spelling). Give either spelling.