What is EXEC_PAJA/.#Misya extracting?
EXEC_PAJA is in fact the Hymn Crystal Purger, which was the overall plot to Phase 1. In  Chanting the Moon ~Tsukikanade~ Ar Tonelico Hymmnos concert Side Kurenai there is a track called EXEC_PAJA/.#Orica extracting.

Orica sounds very much like how Aurica's name is pronounced so one can assume that Misya is supposed to be Misha (they sound much the same as well). Also listening to EXEC_PAJA/.#Orica extracting sounds much like the music that plays when one battles ELMA_DS the first time and the music in the background is supposed to be the Reyvateil Purger was downloaded into sing to prevent ELMA_DS escaping into the Binary Field.

So EXEC_PAJA is the song from the Hymn Crystal Purger and .#Misya extracting indicates it's Misha's version of it. The reason she sings it is so that ELMA_DS won't flee. Just how Misha is singing that and the healing song at the same time is unknown as to my knowledge they can only sing one song at a time.

This is also backed up in EXEC_PURGER's Wikia page where the fourth paragraph says


  Also known by the name EXEC_PAJA/.


The page also lists the unaltered names for both songs matching that of the tracks on the soundtracks, more than likely bring the untranslated romaji from the Japanese Version.