Roberta Flack: The welcome change of pace.During the early 1970s, there was no shortage of powerful female singers across the landscape.Most of them were full of bluesy fire and lava-hot brimstone.  Like a blast of silky-smooth, freshly-crisp air, Flack lowered the temperature a few degrees with her creamy blend of R&B.The prime exhibit of Flack’s ultra-cool charm can be found on the killer tune that won the Grammy Award in 1973 for Record of the Year – the timeless "Killing Me Softly with His Song.”The elegant lady of soul was also a worthy foil for the late, great Donny Hathaway, and the two teamed up for a number of memorable performances, with maybe the ultimate being "The Closer I Get to You.”Aretha Franklin: The Queen of Soul.Aretha has won 20 Grammy Awards, had 20 number one singles on Billboard’s R&B charts, landed 45 Top 40 hits on Billboard’s Hot 100 and was also the first female ever inducted into the Rock-N-Roll Hall of Fame.Aretha, born in Memphis and then raised in Detroit, has moved freely between just about every kind of music form one can think of.From gospel, to R&B, to jazz, blues, rock, pop and even urban contemporary, the great lady has sang it all.Check out: "I Never Loved a Man (the Way I Love You) from the 1967 album of the same name.Etta James: The fiery blues singer.Don’t mess with Ms. Etta James.Beyonce found that out after she sang James’ timeless "At Last” at President Obama’s Inaugural Ball. At a concert performance shortly after that, James said from the stage, "She has no business up there ... singing my song that I’ve been singing forever.” But with James’ track record, she has plenty of ammo to back her up. The owner of four Grammys, 17 Blues Music Awards and a member of the Rock-N-Roll Hall of Fame, James has done it all. From doo-wop to pop to soul to raunchy Chicago blues, James is a living legend with a bigger-than-life voice. And persona to match.Check out: "I’d Rather Go Blind” from 1967’s Tell Mama.Gladys Knight: The Empress of Soul.Considering that they were kicked out of their opening spot on a tour with Diana Ross and The Supremes, because the audience was digging the support act more than the headliners – I’d say they were pretty hot.And the person that gave Knight her walking papers on that tour? None other than Diana Ross herself! However, Gladys Knight & The Pips didn’t waste any time feeling vengeful. They simply went about their business and a few years later hit pay-dirt with the mega-classic "Midnight Train to Georgia.”Full of raw emotion and undying passion, that song was the perfect vehicle to showcase Knight’s incredible vocals.Check out: "Best Thing That Ever Happened to Me” from 1973’s Imagination.Bettye LaVette: The forgotten one.Bettye LaVette’s style is one that’s hard to pin down. Part country, part blues, part gospel and part soul – it occupies its own category.Her vocals cut razor-sharp and hit you right in the gut. They’re rich, emotional and colored with just a tinge of regret and pain.She cut her first album at 16, and in 1972 she signed with Atlantic Records and recorded Child of the Seventies. But due to a lack of interest on the label’s part, it sat un-released until 2006, when it was widely hailed as a masterpiece after over 30 years in the vault.Between those years, the Michigan-born LaVette struggled to stay afloat and battled several personal demons along the way.Cleaned up and focused, LaVette made her big comeback with a pair of outstanding albums – 2005’s I’ve Got My Own Hell to Pay and The Scene of the Crime from 2007.Check out: Talking Old Soldiers from The Scene of the Crime.Sade: The exotic one.There may never again be a voice as irresistibly sexy as the one under the command of Helen FolasadeAdu, better known to the music-loving world at large as simply Sade.Hers has the gravitational pull of the moon. Once it’s locked in on you, forget about it.The next thing you know, all track of time is lost as you drift away on a lush cloud of smooth jazz and R&B, twisted with just the hint of soft, sunny days spent in the Caribbean Islands.Born in Nigeria and raised in Brittan, Sade conquered the American pop charts with a series of seductive singles, starting with "Smooth Operator” off 1984’s Diamond Life.Sade’s smoky, low-key romantic voice is welcome anywhere.Check out: "Please Send Me Someone to Love” from The Best of Sade, released in 1994.Dusty Springfield: The sensual Brit.Take one of England’s leading soul singers of the time. Add Atlantic Records’ super production team of Tom Dowd, ArifMardin and Jerry Wexler. Then send all the above to Memphis, Tennessee in 1969.  The result is the album Dusty in Memphis, widely recognized as one of the top albums of all-time. It was inducted into the Grammy Hall of Fame in 2001.The late Springfield’s voice was soft and mellow, easy on the ears. But at the same time, it was chock full of deep and emotion, forcing you to pay attention.This combination really found its sweet spot when the Rock-N-Roll Hall of Famer tore into southern R&B songs with an orchestrated pop structure to them – as on Dusty in Memphis.Check out: "Son of a Preacher Man” from 1969’s Dusty in MemphisMavis Staples: The voice of the civil rights movement.At the heart of the Staples Singers, once called "God’s Greatest Hitmakers” was Roebuck "Pops” Staples’ youngest daughter, Mavis.Gifted with a seemingly un-limited vocal range, Mavis Staples was also dead-on with her phrasing and could knock your socks off when she sang lead.Straight from the church, the Staples Singers were able to take their message of love and equality to a mass audience after Booker T. &The M.G.’s climbed aboard as the group’s backing band.Still actively touring and recording, Mavis Staples continues to serve as a vocal civil rights activist.Check out: "If You’re Ready (Come Go with Me) from the Staples Singers’ 1973 album, Be What You Are.Tina Turner: The Queen of Rock-N-Roll.Turner has sold almost 200 million records and sold more concert tickets than any other solo performer in history over the course of her amazing career.A career that took off when the Rock-N-Roll Hall of Famer teamed with her infamous husband in the Ike & Tina Revue in the 1960s.On stage she was high-energy all the time, dancing and shimmying while belting out soon-to-be-classics like "Proud Mary” while a swinging R&B band pumped out thick grooves behind her.After a down spell when she parted ways with Ike, Tina found her ultimate success with the massive comeback album Private Dancer, an album of highly-polished pop, in the 80s, and also sang duets with everyone from Mick Jaggar to Bryan Adams to Barry White. But at the very core of Tina Turner lays a bluesy, soulful singer from rural Tennessee, to this day.Check out: "3 O’clock in the Morning Blues” from Outta Season, issued in 1969.Sarah "Sassy” Vaughan: The Divine One.Blessed with a deep, rich voice that probably was also capable of hitting notes associated with an opera singer, the late Sarah Vaughan was magic.Her glistening vocals first got noticed when she won an amateur night contest at Harlem’s famed Apollo Theater when she was barely 18 years old.That led to a stint in Earl Hines’ band in the early 1940s where jazz aficionados began to take serious notice of the New Jersey born singer.Check out: "I’ve Got a Crush on You” from 1957’s Sarah Vaughan Sings George Gershwin.