AN ACR MLG STARTED AN APCH TO THE WRONG RWY.

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INBOUND TO CLT; APCHING OVER SE GATE WITH N OP. INITIALLY PLANNED; BRIEFED; AND SET RADIOS FOR RWY 36R. FIRST CONTACT WITH APCH ADVISED RWY 36L. RE-BRIEFED RWY 36L AND SET UP FMC ACCORDINGLY. FO FORGOT TO CHANGE ILS FREQ AND I DIDN'T CATCH IT. I WAS IN NAV WITH INTERCEPT LEG TO THE MARKER FOR THE L SIDE; AND CLT TUNED MANUALLY SO I COULD MORE EASILY KEEP TRACK OF THE BEARING TO THE STATION AND THE DME. LEVEL 3600 FT; THEN HDG 340 DEGS TO INTERCEPT THE LOC AT 3000 FT OR ABOVE; CLRED FOR THE APCH. MOMENTS LATER; I REALIZED THAT WE HAD INTERCEPTED THE LOC AND WERE STARTING TO DSND ON THE GS. APPROX 3300 FT MSL; APCH ASKED IF WE WERE ESTABLISHED ON THE LOC. AFTER LOOKING AT MY CDI TRACKING LNAV OFF THE FMC FOR RWY 36L AND NOTING ALMOST CTRED AS WELL AS THE FO'S CDI TRACKING THE LOC (CTRED); I RESPONDED AFFIRMATIVE. APCH ADVISED THAT WE APPEARED TO BE HDG FOR RWY 36R; CLRED US TO 2300 FT WITH A L TURN TO CALL THE ARPT VISUALLY. WE BOTH PICKED IT UP MOMENTS LATER AND WERE CLRED TO AN UNEVENTFUL LNDG ON THE CORRECT RWY. I MET THE CTLR IN PERSON SHORTLY AFTERWARD TO EXPLAIN WHAT HAD HAPPENED. HE MENTIONED THAT IT HAD NOT CAUSED ANY DIFFICULTIES AND THAT BEING ALERT TO WHAT HAPPENED TO US WAS PART OF HIS JOB. HE SAID THAT HE COULD HAVE ASSISTED BETTER BY MENTIONING THE NEW ILS FREQ WHEN HE GAVE US THE CHANGE. WHILE THAT MAY HAVE WORKED; IT WAS STILL OUR MISTAKE. I HAD BEEN LULLED INTO COMPLACENCY BY HAVING AN EXCELLENT FO. THE PERCEPTION OF AN EVENTUAL VISUAL APCH AND THE TOTAL FAMILIARITY WITH OUR HOME ARPT. I ALWAYS CHK THE FO'S RADIO SET-UP AND HAD SO BEFORE THE CHANGE IN PLAN. THE NEXT TIME; I WILL BE MORE ALERT; ESPECIALLY AFTER A CHANGE IN PLAN. ALSO; I ALWAYS (AS THE PNF) CHANGE TO THE ILS FREQ SOMETIME DURING THE APCH. NOW I WILL DO SO NO LATER THAN APCH CLRNC WITH AN IDENT.