Here in the 1920 LDS edition, the word directors was replaced by interpreters. The same change was made a few verses later:
Elsewhere the Book of Mormon refers to these directors as interpreters:
On the other hand, the singular director is used systematically in the text to refer to the Liahona:
Also note that the text consistently uses singular function words (a, it, this, and its) to refer to the Liahona. Thus the original Book of Mormon text twice uses the plural directors as a synonym for interpreters, but the singular director refers only to the Liahona. Yet in a revelation given during the translation (in June 1829), the plural term directors was used to refer to the Liahona (although the specific reading here may date from as late as 1835):
This revelation does not appear in the 1833 Book of Commandments (or at least in that part of the book that was printed prior to the press being destroyed). It first appeared in the 1835 Doctrine and Covenants (there it is found in section 42). The term Urim and Thummim used in section 17 of the current LDS Doctrine and Covenants was Joseph Smith’s later designation for what the Book of Mormon generally refers to as the interpreters (although apparently the term Urim and Thummim was sometimes used to refer to the seer stone that Joseph also used in translating). In a letter dated 7 September 1834, written by Oliver Cowdery to William W. Phelps and published in the October 1834 issue of the Latter Day Saints’ Messenger and Advocate (1:13–16), Oliver explained that the term Urim and Thummim referred to the Nephite interpreters:
Day after day I continued, uninterrupted, to write from his mouth, as he translated with the Urim and Thummim, or, as the Nephites would have said, “Interpreters,” the history or record called “The Book of Mormon.”
Yet in Alma 37:21, 24, the Book of Mormon uses the term directors to refer to the interpreters.
The original manuscript is not extant for the first occurrence of directors (in Alma 37:21), but spacing in the lacuna favors directors instead of the somewhat longer interpreters. Moreover, the second occurrence of directors is extant in the original manuscript, so the evidence seems quite strong that the original text in Alma 37 read directors and not interpreters. Nor is there any nearby preceding occurrence of director that could have prompted Oliver Cowdery or Joseph Smith to accidentally replace an original interpreters with directors in 𝓞 (the only previous instance of director is in Mosiah 1:16); the word director for the Liahona does show up in chapter 37, but only later in verses 38 and 45.
Joseph Smith later indicated (in his 1839 History) that the Urim and Thummim were used at the time of the Book of Mormon translation to receive a number of revelations, including sections 3, 6, 7, 11, 14–16, and 17 (the numbering assigned in the current LDS Doctrine and Covenants). In this later account, Joseph wrote as if the Urim and Thummim were the Nephite interpreters, not the seer stone that he also used to translate the Book of Mormon. See Joseph’s commentary before each of these revelations as found on pages 287–295 in Dean C. Jessee, The Papers of Joseph Smith, volume 1 (Salt Lake City, Utah: Deseret Book, 1989).
In other words, the Nephite interpreters had broad revelatory powers: Joseph could use them not only to translate but also to receive personal revelations, with instructions regarding the translation (as in section 3 of the current LDS Doctrine and Covenants). These extended uses of the interpreters to give general directions on what to do suggest that such an instrument could also give, if needed, physical directions (although no instance of this capability is specifically mentioned).
In any event, the plural term directors (at least in its general sense) is an acceptable alternative for interpreters. And we should also note that even the Liahona, consistently referred to in the text by the singular director, was used to receive revelations as well as physical directions:
Ultimately, there is no necessary distinction in the text between the terms directors and interpreters. The critical text will therefore restore the original plural directors in Alma 37:21, 24 since the term is clearly intended.
Summary: Restore in Alma 37:21, 24 the two original occurrences of the alternative term directors in place of the more general term interpreters (used elsewhere in the text); the second instance of directors (in verse 24) is extant in 𝓞, and spacing between extant fragments of 𝓞 supports the original occurrence of directors in the first instance as well (in verse 21); in the original Book of Mormon text, the plural directors is distinguished from the singular director, which refers only to the Liahona.