Here is a brief summary and explanation of the three (not only two) versions of the Masonic Funeral Music. Hope this helps some. Mozart entered the Masonic Funeral Music in his work catalogue "in the month of July [1785]" as "Masonic Funeral Music for the death of Brothers Meklenburg and Esterhazy". The problem here is that Georg August von Mecklenburg-Strelitz died on November 6, 1785, and Franz Esterhazy von Galatha on November 7, 1785. Both deaths were observed in ceremony at the Vienna Crowned Hope Lodge on November 17, 1785.
The theory of Philippe Autexier from the Mozart Jahrbuch of 1984-85 goes like this. The Masonic Funeral Music is dated in the month of July and the next entry, the Piano Quartet in g-minor K478 is dated "ditto" to the Funeral music. This Quartet is dated October 16, 1785 on its autograph. The next entry in the work catalogue is the vocal quartet K479 entered November 5 -- still before the two Masonic brothers died. Thus all three of these pieces were entered after the brothers died -- thus after Nov 7 but before the entry dated November 21, the vocal trio K480. One other important note here is Mozart designated the setting for the Masonic funeral music in his work catalogue for 2 Violins, 2 Violas, 1 Clarinet, 1 Bassetthorn, 2 Oboes, 2 Horns and Basso. In the autograph the piece calls for 2 more Bassetthorns and a Contra Bassoon.
Looking for a dating in July for the funeral music, Autexier found a clue in the Lamentation melody used in the middle of the work. He found the symbols of this theme to brought into connection with the ceremony of elevation to the Master, and a Master whose temple had been destroyed. One such case happened precisely in the summer of 1785 in Vienna. On August 12 Mozart attended the elevation of Carl von Koenig whose Lodge had been forbidden in May by the Inquisition. Autexier hypothesised the music played that day was the music we know as the Funeral Music and was originally wrote for two part Man's choir and orchestra. Two texts are preserved in a song collection that Mozart set to music, on poems of Gottlieb Leon, on this date also. The texts begin with words "In dunkle Schatten eingehulltet" and "Vollbracht ist die Arbeit der Meister".
When the two Masonic brother died, Mozart re-scored this music used for the elevation ceremony for funeral music -- in the setting stated in his work catalogue. Then on December 7, 1785, a second Lodge funeral was given to honor Mecklenburg and the expanded setting was used for this.
In short Autexier proposed three versions of the music;
Two studies have been made since then -- by Heinz Schuler (1992) and Jason B. Grant (2000) suggesting meanings in the music and exactly where played in the Masonic ritual, but I have not read either, so can not comment on them.
Dennis Pajot