It was four years ago today (April 21st, 2016) that Prince — born Prince Rogers Nelson on June 7th, 1958 — died at age 57 of an accidental overdose of the opioid fentanyl. In April 2018, Minnesota's Carver County Attorney Mark Metz announced he was closing the investigation into the musician's death without filing any criminal charges. During a press conference, Metz explained, "For the past two years, law enforcement has conducted an extensive, painstaking and thorough investigation into Prince's death. That investigation determined that Prince died from taking a counterfeit Vicodin pill that contained Fentanyl, a dangerously powerful opioid. . . we simply do not have sufficient evidence to charge anyone with a crime related to Prince's death."

Coming to CBS tonight (Tuesday, April 21st) is Let's Go Crazy: The Grammy Salute To Prince. The two-hour event airs at 9 p.m. ET and PST and features performances by Shelia E., the Time, Earth, Wind, & Fire, Foo Fighters, Common, Beck, H.E.R. and Gary Clark, Jr., John Legend, St. Vincent, and Mavis Staples & The Revolution, among others.

Released last year was the posthumous release, The Originals. The set features tracks recorded between 1981 through 1991 that Prince wrote for others, including such instant classics as Sheila E.'s "The Glamorous Life," the Time's "Jungle Love," and the Bangles’ 'Manic Monday.'" The Originals also features Prince's versions of Vanity 6's "Make-Up," Kenny Rogers’ "You’re My Love," and Prince’s original version of "Nothing Compares 2 U," which Prince's estate first released in April 2018.

2018 saw the release of the first posthumous Prince album, Piano & A Microphone 1983. The set, which was mastered from a cassette tape, has been released as a nine-track, 35-minute album featuring the contents of a previously unreleased 1983 home studio cassette recording of Prince at his piano captured at his Kiowa Trail home studio in Chanhassen, Minnesota by engineer Don Batts.

According to the press release, "The private rehearsal provides a rare, intimate glimpse into Prince's creative process as he worked through songs which include '17 Days' and "Purple Rain' (neither of which would be released until 1984), a cover of Joni Mitchell's 'A Case Of You,' 'Strange Relationship' (not released until 1987 on his critically acclaimed Sign O' The Times album), and 'International Lover.' The album also includes a rare recording of the 19th Century spiritual 'Mary Don't You Weep,' which was featured during the end credits of Spike Lee's recent film, BlacKkKlansman. For fans of Prince's spontaneous live medleys, tracks one to seven of the album are presented in that same format as they were originally recorded."

In the year following his death, the "Purple One’s" catalogue sold a combined 7.7 million copies in the U.S. alone, according to Nielsen. Of that 7.7 million, 2.3 million came in the form of traditional album sales, while the remaining 5.4 million were from digital downloads — with Prince, by far, selling more albums than any other artist during the same time period. The closest competition was Adele, who sold an impressive 2.23 million units. Billboard reported the 5.4 million digital song downloads comprise one-third of the 18.64 million downloads of his songs since Nielsen began tracking that info in 2003.

Since his passing, fans have found a number of other ways to celebrate Prince’s life as well. His Paisley Park home/studio complex in suburban Minneapolis has been turned into a museum, with his ashes on display in a glass and ceramic Paisley Park-shaped urn.

When we last spoke to Cyndi Lauper, she was still reeling from Prince's death. Aside from their friendship, Lauper was a major fan of his and covered his Dirty Mind classic "When You Were Mine" on her 1983 breakthrough album, She's So Unusual. Lauper, who had lost touch with Prince in recent years, regretted not being aware of his whereabouts prior to his death: ["I'm pretty devastated, because you just didn't expect him to go like that. He doesn't do drugs. He was sick, so, y'know, he might've been taking medication and I don't know, what the heck happened. And, y'know, he always pushed himself — he pushed, y'know? I feel horrible. I was in Minnesota, I didn't call. I didn't know where he was anymore. I didn't know if he was in Minnesota, or Toronto. One time he's in Toronto, then he's in L.A. I didn't know he kept a place in Minnesota, y'know? And I should've — 'cause I was there — called."] SOUNDCUE (:35 OC: . . . was there called)

Bruce Springsteen — like most of rock's upper echelon — including Paul McCartney, Bob Dylan, Mick Jagger, Pete Townshend, and Elvis Costello — remained a die-hard fan and in awe of Prince's output: ["It's funny, because I was just talking to someone who was talking about Prince, who makes. . . writes a lot of music. He's tremendously prolific. And I find everything he does. . .  I find is fascinating in some fashion and filled with just enormous creativity. He's just a. . . And I envy his prolific-ness. And I made records as quickly and as often as I could. I would've loved to have made more records. I wished I had put out more records and more music, y'know?"] SOUNDCUE (:25 OC: . . . more music y'know)

Country star Keith Urban told us that above the hitmaker, or the star — it was the musician above all else that captivated him: [“The very first time I saw him was on MTV, y'know? ‘1999,’ I guess was the song and video. That period you saw so many artists come and go, one hit wonder sort of thing, but there was something immediate about that track and about him and the way he performed. It was no surprise that that was going to be something of legend. That catalog of his is just mind-blowing. You kind of have to ask guitar players about Prince, because most people don’t seem to know (about his guitar playing), but every guitarist I’ve ever talked to knows he was a monster on guitar. Certainly when you went and saw him live, you’re just like, ‘Oh my God!!! That’s you!!! You played on the records?! Oh my God!!!’] SOUNDCUE (:47 OC: . . . oh my God)

Sheila E., both a romantic and musical partner to Prince over the years, spoke lovingly about the good times with her dear friend: ["Well, there are too many, so, probably I'd just say, just being his friend. We just had a great time. Y'know? We were really, really good friends. And we just loved to have fun. And we did."] SOUNDCUE (:10 OC: . . . and we did)

PRINCE ON PRINCE

Prince accepts The Lifetime Achievement Award at the 2010 BET Awards:

["I do believe the future is in good hands. I have seen so much talent here tonight. I was watching back stage and at the hotel and I'm just so thankful to be a part of this world of music. I was pretty wild in my younger days. And you don't have to do what I did, you don't have to make any of the mistakes I made. The future is in your hands now, the world is really yours. There's a change in America that's going on right now and everyone can feel it and we are going to be the beacon to the rest of the world. Thank you so much to Debra Lee and thank you Steven Hill for a wonderful night tonight. I will never forget it, as long as I live. Thank you so much."] SOUNDCUE (:48 OC: . . . thank you so much)

Prince speaks on the music industry at NAACP Image Awards in 2007:

["And I would just challenge the phone companies and the new digital providers to allow us to be the gatekeepers to stewards the new jazz renaissance, hip-hop and soul music in the twenty-first century rather than the accountants and lawyers who ruined the music industry this first time around."] SOUNDCUE (:19 OC: . . . first time around)

Prince accepts Best Male R&B Artist at the 2006 BET Awards:

["This was unexpected but I appreciate it nonetheless. I'd like to give all praise and thanks to Jehovah God for the gift of life and music. Also I'd like to take this time to thank Chaka Khan, Stevie Wonder, India.Arie and Yolanda Adams for continuing to be such inspiration in my life. I thank you so much for this BET, peace."] SOUNDCUE (:28 OC: . . . this BET peace)

Prince in 2000 on his records sales: 

["I always get journalists saying to me, 'You're not selling as many records as you used to.' And I say, 'Well, I never sold the records — I only made 'em. You gotta talk to the accounting firm on that.'"] SOUNDCUE (:09 OC: . . . firm on that)

Prince says he never concerns himself with sales figures :

BET AWARDS Prince Accepts Best Male R&B Artist :

NAACP IMAGE AWARDS Prince Accepts Award :

Prince Wins Lifetime Achievement Award :

Sheila E. Recalls Spending Time With Prince :

Keith Urban On Prince :

Bruce Springsteen On Prince And Being Prolific :

Cyndi Lauper On Prince’s Death :