'The Voice' Season 9 Premiere: Everything To Know About The New Judges Panel Before The Show Kicks Off On Sept. 21

Although it feels like it just ended, “The Voice” is returning to NBC on Sept. 21 with an all new season and an all new crop of amateur and celebrity performances. Luckily for those that like to remain ahead of the curve, NBC has been teasing what fans can expect from Season 9 of the singing competition for weeks.

First of all, the biggest change between Season 8 and Season 9 will be in the middle judge’s chair. After taking a season-long break, Gwen Stefani is returning to the show to replace Christina Aguilera as the fourth coach on the celebrity panel. She’ll join returning coaches Adam Levine, Pharrell Williams and Blake Shelton.

Luckily for those that want more star power injected into the two night weekly series in Season 9, NBC has you covered. As with previous seasons, “The Voice” will employ the use of celebrity guest mentors for each of the four teams. It was previously reported that Selena Gomez will join Team Gwen at some point in the competition to help her singers advance ahead of their competition. Meanwhile, Missy Elliot will join Team Pharrell and bring her unique brand of musical prowess to his 2015 team. According to Rolling Stone, country-singer Brad Paisley has been tapped to help his friend, and fellow country star, Blake Shelton and his team. Finally, People reports that Adam Levine will be joined by Creedence Clearwater Revival front man John Fogerty, who previously took “The Voice” stage last season to sing a duet with winner Sawyer Fredericks.

If those eight celebrity musicians aren’t enough to satiate your desire for more star power in Season 9, perhaps Rihanna will. It was previously reported that the “American Oxygen” singer will be joining all four teams as a “key advisor.” It’s unclear exactly what this means, but it’s possible that Rihanna will be used like Reba McEntire was in Season 8. The country singer sat in on rehearsal sessions for each one of the teams’ remaining contestants and offered advice and tips to help them win. Unfortunately, odds are good fans will have to wait until later in the competition when the teams are more solidified with fewer members before Rihanna offers her coaching.

However, what viewers can look forward to in the premiere episode is a performance by all four coaches to open the evening. The video below shows each of the four celebs taking on one another’s hit songs. Stefani gets things started with Shelton’s “Neon Lights.” Blake follows with the No Doubt rocker’s “Don’t Speak.” Pharrell Williams takes the stage next singing Maroon 5’s “Sugar” and Adam Levine closes things out with Daft-Punk and Williams’ collaboration “Get Lucky.”

Watch "The Voice" Season 9 premiere on Monday, Sept. 21 at 8 p.m. EDT on NBC. Will you be tuning in? Comment below or tweet your thoughts on the blind auditions to @TylerMcCarthy.