GA pilot reported a ground conflict resulting in an aborted takeoff as another aircraft was taking off at the opposite end of the same Runway. The reporter was not on the correct CTAF frequency which was the cause of the conflict.

Narrative

I am self-reporting as PIC of Aircraft X. I was parked at the north runup area of LMO near approach end of Runway 11. Was waiting for favorable winds at destination airport. After receiving favorable weather report; I performed a quick start + runup; reviewed checklists; and proceeded directly to depart full length Runway 11. I had not seen nor heard any traffic in the pattern in the last 10 min. After starting takeoff run; I saw another aircraft taxi and landing lights departing Runway 29 at other end of the field. Confused; I aborted takeoff and pulled off the far north edge of the Runway before reaching midfield taxiway. Aircraft Y proceeded with takeoff and was airborne well prior to my position. I exited midfield and eventually realized that my radio was tuned to the wrong frequency - I had incorrectly transcribed a Comm Box 'cheat sheet' from the VFR sectional; so did not hear Aircraft Y departure call nor did he hear mine (nor any other traffic in the past 30 min). I proceeded to Runway 29 departure end; eventually made contact with Aircraft Y and explained the situation and apologized and proceeded uneventfully to destination. Cause - Not referencing current publication for CTAF. Didn't properly clear the Runway before takeoff roll. Both Aircraft X and Aircraft Y had taxi and landing lights turned on; which got my attention much sooner for the abort decision. Other contributing factors: bad winds; recent divert; lack of recency in this particular tail # for comm panel; non-standard taxi direct from run-up area; hurried mentality for late arrival. Corrective fix - I will add a comm check to my regular taxi and letdown/arrival checklist.