FLC OF LTT FAILED TO OBTAIN TWR LNDG CLRNC.

Narrative

THE INCIDENT TOOK PLACE ON THE FINAL LNDG AFTER 6 LEGS; 14 DUTY HRS AND 8 FLT HRS. FLT PFN TO ATL WAS BEING VECTORED TO ATLANTA HARTSFIELD BY ATLANTA APCH CTL FREQ 127.9. JUST PRIOR TO THE OTHER MARKER FOR RWY 9R WE WERE SWITCHED TO APCH 118.35. AT THAT POINT WE WERE TOLD TO KEEP OUR SPD UP AS LONG AS POSSIBLE FOR INTRAIL TFC. ALSO WE WERE LNDG BEHIND A (ACR) 757. WE INTERCEPTED THE LOC AND GS VISUAL. I WAS GOING THROUGH LNDG CHKS AND WAITING FOR FLAP SETTING COMMANDS. I WAS EXTREMELY BUSY AND NEGLECTED TO SWITCH TO TWR 119.1. WE WERE IN FINAL CONFIGN AT 500 FT AGL. THE TFC AHEAD HAD CLRED THE RWY SOME TIME AGO. THE CAPT MADE A NORMAL LNDG AND EXITED AT THE FIRST HIGH SPD. I REALIZED MY MISTAKE WHEN I LOOKED AT #1 RADIO WHICH STILL HAD 118.35 APCH CTL DIALED IN. I SWITCHED TO TWR AND RPTED HOLDING SHORT OF RWY 9L AT B6. TWR THEN CLRED US TO CROSS AND TAXI TO OUR ASSIGNED RAMP. I FEEL CONTRIBUTING FACTORS FOR THIS OVERSIGHT WAS CREW FATIGUE. IT HAD BEEN A VERY LONG DAY. ON THE FINAL LEG WE ALSO HAD TO PENETRATE A LINE OF VERY HVY TSTMS; WHICH FURTHER CONTRIBUTED TO MENTAL FATIGUE. ALSO BEING VECTORED IN FOR A SHORT APCH WHILE BEING ASKED TO MAINTAIN HIGH AIRSPD SIGNIFICANTLY ADDED TO THE CREW'S WORKLOAD.