Johnny's musical career began in the early '80s after forming the band Phaze with his older brother, Joey. The band underwent reform and he started drumming with the band Killerhit in 1983 at the age of 16?. Sharing vocal duties with Joey the four-piece act hit the East Coast club circuit with an enormous amount of success, earning enough by 1987 to purchase their own lighting rig, truck and tour bus (purchased from Jimmy Buffett).

Re-locating to Hollywood, Killerhit hooked up with Poison's Bret Michaels. The singer gave them his former publicist Debra Rosner's number who instantly became the band's manager. Realizing the need for a front man, Johnny vacated the drum stool for center stage, Las Vegas native Darek Thomas Cava taking his place behind the drum kit. Soon after, the band realized there was not a single blonde among them, and changed their name to the more appropriate Brunette. The band broke The Doors and Van Halen's single-weekend attendance records on the Sunset Strip in Hollywood CA. Their sensation soon brought attention and admiration to the recording industry. They were courted by top record executives for months. The band had built a loyal worldwide fan base. Differences began to develop in the Brunette camp before a recording deal could be secured, and the band decided to call it quits in 1991. Gioeli then started working with his brother Joey on songs for an album they were going to call Brothers. However, Neal Schon, Journey's guitarist (who was dating their sister at the time) met with them and asked if he could play with them, and they agreed. Then, in 1992, they released their first effort, entitled Double Eclipse, and called themselves Hardline, which was moderately successful but not enough to get into the mainstream, especially considering its post-Nirvana release. After this they began writing songs for a second album but once again called it quits while recording the songs due to troubles with their manager and Neal Schon. Johnny had all but disappeared from the music scene until, in 1998, German guitarist Axel Rudi Pell found himself in need of a vocalist after the departure of Jeff Scott Soto. Axel had admired Johnny for a long time, stating he always thought Johnny's vocals would go well with his music. Axel eventually found means of contacting Johnny and flew him to Germany to record vocals for his Oceans of Time CD, which up to date has been considered as one of the best Axel Rudi Pell albums. He is now the permanent lead vocalist of the band and shows no signs of leaving.

He also participated in Michael Voss's compilation album titled Voices Of Rock - MMVII, released the 07.20.2007 on which he performed the song "Phoenix Rising". In 1994, Johnny also collaborated with musician Doug Aldrich, who had performed live as Brunette's guest guitarist, and performed the vocals for the song "Face Down" featured on Aldrich's Highcentered album, later included again on Aldrich's 2002 album Alter Ego.