The narrator, Keitin Avram, and a number of other characters in Rebel Heart are bilingual in Basic and Old Alderaanian. This language (on its own terms Karmeth, meaning 'speech') survived on Alderaan at the period of the Empire both as a literary and ceremonial tongue, and (in a more colloquial form) as the vernacular of the country people and elderly. Until comparatively recently this was the usual language on Alderaan—it was Bail Organa's cradle-speech, as his nanny (Miridh Arodessa, later Avram) was country-bred, and did not learn Basic till her teens. Leia Organa's generation (most of the characters of this story) spoke Basic in general, but were usually taught Alderaanain also. The Avram children, for example, spoke Basic to each other and Karmeth to their grandmother. Tycho Celchu, being city-reared for generations, was a little rusty. After Alderaan's destruction, there was a resurgence of interest in their ancestral language among the exiles.

Pronunciation: ch and gh are gutteral sounds, as in Gaelic. bh is v. dh is a voiced th, as in that. Karmeth was written in a slightly modified form of the Aurebesh letters and tended to change slightly in transliteration to Basic, losing the accent used to mark short vowels. (à è ì ò ). Keitin would have spelt her name in her own alphabet Keitìn Abhram, and the very name Alderaan was originally Àlderan, though this transliteration was so old it was usually used even when writing in Alderaanian letters. In this story, the Basic versions are used in almost all cases.