Andra Day. Nicki Minaj. Blake Shelton. The Weeknd. What do these seemingly disparate artists have in common? They all had mentors to guide them on their musical journey.

Merriam-Webster defines mentor as "someone who teaches or gives help and advice to a less experienced and often younger person." But the meaning behind the word has roots all the way back to the ancient Greek poet Homer. In his epic poem "Odyssey," the protagonist Odysseus leaves behind his family to fight in the Trojan War and entrusts his household to Mentor, who serves as the teacher and caretaker of Odysseus' son, Telemachus.

History offers plenty of examples of nurturing mentor/mentee relationships across a variety of disciplines. Socrates and Plato, Hayden and Beethoven, Frank Marshall Davis and President Barack Obama, and George Martin and the Beatles. In music, mentoring takes many forms, from a one-shot golden opportunity to continuous learning. It refines music- and business-related abilities, builds life skills, and defines character.

The career of GRAMMY-nominated R&B vocalist Day took off when she became a protégé of Stevie Wonder. Day says Wonder consistently set the example of putting pure joy into music-making, reminding her to maintain her enthusiasm and never forget that "you love what you do."

Mentoring isn't something that came naturally to Shelton, a current coach on "The Voice." He's stated that his own mentor, Trace Adkins, gave him a head start on how it's done. Paying it forward, Shelton has helped "The Voice" contestants with whom he's made a strong connection. He recorded "My Eyes" with season two contestant Gwen Sebastian and took the runner-up of season one, Dia Frampton, on tour as his opening act.

GRAMMY winner The Weeknd got a huge career boost after he co-wrote and co-produced songs on Drake's Take Care album, and later after being showcased by Drake in concert. Drake has rapped about Lil Wayne being his mentor early in his career, and Nicki Minaj has acknowledged Lil Wayne as her own mentor after he discovered and signed her to his label in 2009.

GRAMMY winner Skrillex helped fellow EDM artist and GRAMMY winner Zedd find his voice. After Skrillex happened across a track Zedd had sent him online, he invited the younger artist to tour with him. Hesitant to engage the crowd, Zedd found confidence and built his stage presence thanks to Skillex's mentorship.

Eminem famously thanked Dr. Dre on "I Need A Doctor": "All I know is you came to me when I was at my lowest. You picked me up, breathed new life in me. I owe my life to you."

And Eminem wasn't Dr. Dre's only protégé. Dre took fellow Compton, Calif., rapper Kendrick Lamar under his wing. Now Lamar tries to pay this forward for the next generation of musicians who look up to him.

"[Dr. Dre] has always been that mentor, letting me know the mistakes that he's made," said Lamar in a GRAMMY.com interview. "[I] try not to make the same mistakes, so I always have to take that into consideration for the next kid that's looking at Kendrick Lamar as their Dr. Dre."

With the rise of social media, mentoring can take shape through electronic encouragement, as with Taylor Swift's tweets praising country singer/songwriter Kelsea Ballerini. The two developed a friendship alongside their professional relationship, and Ballerini has admitted Swift sends career advice to her via text.

Some mentoring relationships can last for decades. Renowned guitarist Steve Vai's drummer, Jeremy Colson, is one link in a nearly 45-year-long chain of mentoring, beginning in the 1970s with Vai's mentors, GRAMMY nominee Joe Satriani and GRAMMY winner Frank Zappa.

Colson confides that GRAMMY winner Vai has been far more than a mentor: "[He has] seen me close to death from drugs and alcohol and helped me reclaim my life."

Musically, Vai has guided him to play up to his full potential, Colson says, having taken him from a "young, green kid to a seasoned touring drummer and directing my choices both musically and personally. The greatest gift Steve's ever given me is introducing me to the present moment. It helps me navigate my life in every way."

Colson is the beneficiary of knowledge Vai began attaining at age 12 from his first mentor, a then-16-year-old Satriani. "My guitar lessons with Joe were the most important thing in the world," Vai remembers. "I was like a sponge, and he was the ocean."

Vai admits he had low self-esteem and was well below average in all school subjects except music and math. He had difficulty with memorization, and after Satriani assigned him to memorize all the notes on every guitar string, Vai tried to bluff his way through. Satriani immediately sent him home.

"Joe did not tolerate slacking off," says Vai. "As I walked home, I made a solemn pledge that whatever was in my lesson every week, I would learn it cold and go above and beyond. So a little tough love went a long way, because I never stopped feeling that wonderful drive." 

The self-discipline, preparedness and positive attitude he developed with Satriani formed the basis for Vai's next mentoring relationship. Though Satriani had been a tough taskmaster, the late Zappa is notorious in music history as the most exacting of all.

Vai was 18 years old when he began the arduous work of transcribing Zappa's complex music, and Vai had to invent notation to signify Zappa's own musical inventiveness. At 20, Vai — transitioning from transcriber to touring guitarist — joined Zappa's band as his youngest-ever member. Affectionately nicknamed "my little Italian virtuoso," Vai received album credit for playing "impossible guitar parts."

"I got to work for a man whose creative instincts were constantly firing, and he was always envisioning and creating," Vai says. "Musically, I learned that if you have what you feel is a good idea, just do it.

"There isn't a day that goes by where I don't see how what I've learned from him flows into my everyday decision making," Vai continues. "When I think about all these things, it's as if he's here for me and continuing to mentor me."

When Vai was a guitarist in Zappa's band during the 1980s, the mentor asked him to teach his son Dweezil, then a 12-year-old beginner on guitar. Vai instructed the younger Zappa on technique and showed him how to avoid bad habits on the instrument.

Over time, Dweezil Zappa has distinguished himself as a world-class guitarist who now mentors others through his own Dweezilla Music Boot Camp. In one component of his camp, he assembles the participants into a full guitar orchestra. By mixing discussion sessions with hands-on guitar demonstrations, Dweezilla instructors mentor each other along with attendees.

In music and in life, Zappa integrates a key perspective he learned from his father: "You have to look at everything as an opportunity to improve, and there's more than one way to accomplish a goal."

That's an outlook also incorporated by Vai in his prearranged gatherings with fans before many of his concerts. In these meetings, Vai customizes his counsel for each participant. "I'm inevitably asked for advice, and I always do my best to put myself in their position when responding," he says.

These times are among his favorite elements of touring. Vai says he always enjoys speaking to young people because "there's a glorious sense of innocence, freedom and positive expectation. They're discovering their independence and are ready to live the dream."

In the manner of Wonder, Vai emphasizes that the best wisdom any mentor can pass on is to "follow your bliss, find the thing that excites you the most, and throw yourself into it.

"Mentoring or being mentored is really a two-way street," he says. "You learn what you teach."

(Laurel Fishman is a communications and marketing professional, specializing in writing and editing for entertainment media and a wide range of areas. She is an advocate for the benefits of music making, music listening, music education, music therapy, music-and-the-brain research, and music and interdisciplinary studies.)