We don't have synonyms for intramental yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are instrumental, incremental and intermental.
°(music) Pertaining to, made by, or prepared for, an instrument, especially a musical instrument; as, instrumental music, distinguished from vocal music.
"He defended the use of instrumental music in public worship. — Thomas Babington Macaulay"
°(music) Pertaining to, made by, or prepared for, an instrument, especially a musical instrument; as, instrumental music, distinguished from vocal music.
"He defended the use of instrumental music in public worship. — Thomas Babington Macaulay"