EMB ERJ 145 ER/LR
Situational Awareness
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented
Human Factors
While intercepting the localizer to Runway 27R; the Captain acting as flying pilot became confused and turned in the frequency to the localizer for Runway 27L.  This action was caught immediately by the flight crew and also ATC.  ATC remarked with; 'verify that you are in the turn to intercept 27R.'  This confusion had all taken place quite a distance from the field before an Approach Checklist could be run; where the  mistake would have also been identified.  An immediate action was taken place and the correction was made; there was no further remarks from ATC.
EMB-145LR First Officer reported Captain selected the wrong localizer frequency on approach to ORD that led to a small lateral deviation before the crew and ATC noticed.