Just curious, RBRadioWaves, apparently you were picking up some radio waves other than Lite FM 106.7 NYC since Marvin Gaye's "Mercy Mercy Me" did not air on WLTW NYC at any time on 1/21/12. The only Marvin Gaye song that did air was 1982's "Sexual Healing" at 2:18am. The Phil Collins song "Take Me Home" was airing on Lite FM at the time of your posting on Sat. evening 1/21/12. It's also a "Best Of The '80s" weekend on Lite FM - link:
http://www.1067litefm.com/pages/80s/
Perhaps you heard a song that "sounds like" "Mercy Mercy Me" or you were tuned to another station. For example, songs that were playing on other NYC area stations at the time of your posting:
a song with a somewhat similar social theme - Stevie Wonder's "Living For the City" (late 1973 into early 1974) - was playing on WHUD-FM-100.7 Peekskill, NY.
This one's a stretch, but hey, ya never know, the choruses are "somewhat" similar: OneRepublic's "Good Life" was playing at that time on Fresh 102.7 WWFS-FM NYC.
I also checked the Mediabase log for Lite FM for the day of 1/21/12 and have checked on other days since this thread has started. Your second point is correct (which admittedly is the main thrust of your post): the only 1970s song I could find for 1/21 was "Cruel To Be Kind" by Nick Lowe (1979) which aired at 7:08pm. Other days have similar results - maybe 1 song per day, occasionally during the Delilah evening request show ("You Are So Beautiful" - Joe Cocker - 1975 comes to mind).
Is it possible there's missing song entries from the Mediabase log? Sure. But generally they're more accurate and thorough than the Yes.com site's logs. And there were a couple of stations with no song history lists to look at. Just mentioning that some folks "hear" a version of some things (songs, news, info, etc.) that may not be what was actually broadcast.
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Station playlists for 1/21/12 - evening to maybe jog your memory:
WLTW-FM-106.7 New York (AC) "LiteFM" Powered by MEDIABASE®
Time Played Artist - Title - Label - Year
8:59 PM MR. MISTER - Broken Wings - RCA '85
8:55 PM FRAY - How To Save A Life - Epic '06
8:52 PM ROMANTICS - What I Like About You - Nemperor '80
8:44 PM BRANIGAN, LAURA - Gloria - Atlantic '82
8:40 PM TRAIN - Hey, Soul Sister - BNA/Columbia - '10
8:35 PM COLLINS, PHIL - Take Me Home - Atlantic '86
8:30 PM ADELE - Someone Like You - XL/Columbia '11/'12
8:26 PM LAUPER, CYNDI - All Through The Night - Portrait '84
8:22 PM KOOL & THE GANG - Celebration - De-Lite '81
8:12 PM MADONNA - Lucky Star - Sire '84
8:08 PM BLACK EYED PEAS - I Gotta Feeling - Interscope '09
8:04 PM BERLIN - Take My Breath Away - Columbia '86
7:59 PM U2 - With Or Without You - Poly./PLG '87
7:53 PM MICHAEL, GEORGE - Father Figure - Columbia '88
7:50 PM UB40 - Red Red Wine - A&M '84 + '88
7:47 PM BANGLES - Eternal Flame - Columbia '89
7:43 PM FURTADO, NELLY - Say It Right - Mosley/Geffen/Interscope '06/'07
7:39 PM JOURNEY - Faithfully - Columbia '83
7:35 PM FRANKIE GOES TO HOLLYWOOD - Relax - Poly./PLG '85
7:31 PM WILLIAMS, DENIECE - Let's Hear It For The Boy - Columbia '84
7:27 PM A-HA - Take On Me - Warner Bros. '85
7:23 PM POLICE - Every Breath You Take - A&M '83
7:19 PM CLARKSON, KELLY - Mr. Know It All - 19/RCA '11
7:15 PM HEART - These Dreams - Capitol '86
7:12 PM LENNON, JOHN - Woman - Geffen '81
7:08 PM LOWE, NICK - Cruel To Be Kind - Columbia '79
7:04 PM KEYS, ALICIA - Empire State Of Mind Pt. II - J/RMG '09/'10
7:00 PM COLLINS, PHIL - Sussudio - Atlantic '85
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WWFS-FM-102.7 New York (AC) "Fresh 102.7" Powered by MEDIABASE®
Time Played Artist - Title - Year
9:01 PM GYM CLASS HEROES - Stereo Hearts f/Adam Levine '11
8:57 PM PERRY, KATY - E.T. - '11
8:54 PM DEGRAW, GAVIN - Not Over You - '11/'12
8:50 PM BEYONCE - Irreplaceable '06/'07
8:46 PM FRAY - You Found Me - '08/'09
8:37 PM ONEREPUBLIC - Good Life - '11
8:33 PM SIXPENCE NONE THE RICHER - Kiss Me - '99
8:29 PM DAY, HOWIE - Collide - '04
8:26 PM RIHANNA - We Found Love f/Calvin Harris - '11/'12
8:22 PM CAILLAT, COLBIE - Fallin' For You - '09
8:19 PM SISTER HAZEL - All For You - '97
8:09 PM KINGS OF LEON - Use Somebody - '10
8:05 PM NATHANSON, MATT - Come On Get Higher - '08
8:01 PM ADELE - Someone Like You - '11/'12
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WHUD-FM-100.7 Peekskill, NY (AC) "Westchester and the Hudson Valley's Music And Information Station" - "One great song after another!" Powered by MEDIABASE®
Time Played Artist - Title - Label - Year
9:01 PM TOTO - Hold The Line - Columbia '78
8:51 PM LITTLE RIVER BAND - The Night Owls - Capitol '81
8:37 PM WONDER, STEVIE - Living For The City - Tamla '73/'74
8:33 PM GRAMM, LOU - Just Between You And Me - Atlantic '89
8:28 PM JOHN, ELTON - Philadelphia Freedom - MCA '75
8:22 PM WHAM! - Careless Whisper - Columbia '84
8:13 PM WAR - Low Rider - United Artists '75
8:09 PM WINWOOD, STEVE - Back In The High Life Again - Poly./PLG '87
8:06 PM KC & THE SUNSHINE BAND - Shake Your Booty - Independent '76
8:02 PM ESTEFAN, GLORIA - Everlasting Love - Epic '95