APCH TO WRONG RWY INITIATED BY FLC. WRONG ILS FREQ SELECTED. MOST MAJOR ARPTS HAVE DIFFERENT FREQS IN THE FIRST 3 DIGITS. MIA AND SEVERAL OTHERS DON'T IN THEIR SELECTION FOR FREQS ON PARALLEL RWYS.

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WE WERE INBOUND FROM GRAND CAYMAN TO MIA. WE HAD BEEN DEVIATING AROUND CELLS SINCE WE HAD REACHED THE SOUTHERN TIP OF FL. MIA INTL WAS LNDG E; AND A LARGE CELL WAS AT THE EDGE (SE) OF THE ARPT; ALONG WITH SMALLER RAINSHOWERS TO THE W. WE WERE GIVEN AN APCH CLRNC FOR THE ILS TO RWY 9R; AND WERE GIVEN AN INTERCEPT HDG TO INTERCEPT THE LOC OF ABOUT 60 DEGS OFF OF THE LOC COURSE; APPROX 030 DEGS. THE FO WAS FLYING THE ACFT AND I WAS CONCERNED WITH A CELL THAT HAD BEEN ON THE FIELD AND AT THE TIME WAS LOCATED AT THE SE BOUNDARY OF THE ARPT. I WAS OPERATING THE ACFT RADAR WHILE LOC INTERCEPTION WAS TAKING PLACE. I HAD SET UP MY RADIOS TO IDENT GRITT; THE INITIAL APCH FIX (MIA VOR 183 DEG RADIAL). I HAD LOOKED OVER AT THE FO'S RADIOS AND HAD SEEN THE PROPER INBOUND COURSE DIALED IN AND A FREQ OF 110 SOMETHING. HE INTERCEPTED THE LOC AND I CONTINUED CHKING THE LOCATION OF THE CELL AT THE ARPT. BEFORE WE GOT TO GRITT; THE APCH CTLR TOLD US TO TURN R 20 DEGS AND INTERCEPT THE RWY 9R LOC. IT WAS AT THIS TIME I REALIZED THAT MY FO HAD TUNED IN 110.3 INSTEAD OF 110.9; THE LOC FOR RWY 9R. WE HAD INITIALLY BEEN ON THE LOC FOR RWY 9L. FORTUNATELY; APCHS WERE NOT BEING MADE ON THAT RWY AT THE TIME. THE APCH AND LNDG WERE MADE UNEVENTFULLY. I THINK A MAJOR CONTRIBUTING FACTOR TO THIS INCIDENT IS THE FACT THAT BOTH LOC FREQS FOR LNDG IN THE SAME DIRECTION START WITH 110. (110.9 FOR RWY 9R AND 110.3 FOR RWY 9L). INTERESTINGLY ENOUGH; BOTH LOC FREQS LNDG TO THE W START WITH 109. (109.5 FOR RWY 27L AND 109.1 FOR RWY 27R). THIS IS EXTREMELY UNUSUAL; AND I DON'T RECALL ANOTHER LARGE ARPT WITH PARALLEL RWYS HAVING THE SAME SIT. WHILE IN MY AIRLINE CAREER I HAVE SEEN THE WRONG LOC FREQ DIALED IN; I THINK THIS SIT IN MIA MAKES IT MUCH MORE EASIER TO DO IT. THE FINAL APCH SEGMENT IN A 2 MAN AIRPLANE IS QUITE BUSY; AND WHILE I DO NOT EXCUSE MYSELF FOR NOT CATCHING THIS ERROR; I THINK THIS COULD EASILY HAPPEN AGAIN IN MIA. I AM CONCERNED THAT IF IT DOES HAPPEN AGAIN; SAFETY COULD BE SEVERELY COMPROMISED IF SIMULTANEOUS APCHS WERE BEING CONDUCTED.