Question: What musical role do Kevin Cronin of REO Speedwagon, and Jimmy Gestapo of Murphy's Law share in their respective bands?

Context articles: Ridin' the Storm Out
Kevin Cronin
R.E.O. Speedwagon (album)
Jimmy Gestapo
Caught in the Game
Don't Let Him Go
I Do' Wanna Know
Keep On Loving You (song)
You Can Tune a Piano, but You Can't Tuna Fish
I Needed to Fall

Ridin' the Storm Out is the third studio album by REO Speedwagon, released in 1973.
 It peaked at number 171 on the Billboard 200 chart in 1981, and reaching platinum status in 1989.
 It was the first album to feature Mike Murphy on vocals.
 The sessions started out with Kevin Cronin, but he left the band before the album was finished, due to creative differences.
 The title track would later become a hit for the band on their live album, after Cronin had returned to the band.
 The song refers to the band being stuck in a harsh winter blizzard after a show in Boulder, Colorado at a bar named Tulagi's (now closed).
Kevin Patrick Cronin (born October 6, 1951) is the lead vocalist, rhythm guitarist, and occasional pianist for the American rock band, REO Speedwagon.
 REO Speedwagon had several hits on the "Billboard" Hot 100 throughout the 1980s, including two chart-toppers written by Cronin: "Keep on Loving You" (1981) and "Can't Fight This Feeling" (1985).
R.E.O. Speedwagon is the debut studio album by American rock band REO Speedwagon.
 Released in 1971, it was the only album recorded with singer Terry Luttrell until Kevin Cronin joined the band for "R.E.O./T.W.O." This album concluded with one progressive rock song unlike the later arena rock songs that made them famous.
James Drescher (born December 10, 1960), better known as Jimmy G or Jimmy Gestapo and also known as Jimmy Spliff, is the lead singer for New York based hardcore punk band Murphy's Law.
Caught in the Game is the fourth album by American rock band Survivor, released in September 1983.
 It features guest appearances by Mr. Mister's Richard Page and REO Speedwagon's Kevin Cronin.
 It is the band's last album to-date to feature lead vocalist Dave Bickler, who left due to vocal surgery; despite the fact that he rejoined the band between 1993 and 2000, and again in 2013.
"Don't Let Him Go" is a song written by Kevin Cronin.
 It was originally released as the opening song for REO Speedwagon's #1 album "Hi Infidelity".
 It was also released as a single, reaching #24 on the "Billboard" Hot 100 chart.
 "Don't Let Him Go" has appeared on several REO Speedwagon greatest hits albums.
"I Do' Wanna Know" is a song written by Kevin Cronin that was the lead single from REO Speedwagon's 1984 album "Wheels Are Turnin'".
 It was more of a rocker reminiscent of the songs REO Speedwagon had released in the 1970s than the ballads the band had been successful with in the early 1980s.
 It had limited success on popular music charts, which was blamed for delaying sales of the album until the release of the follow up single, the ballad "Can't Fight This Feeling."
 The video to the song was nominated for several awards.
"Keep On Loving You" is a soft rock power ballad written by Kevin Cronin and performed by American rock band REO Speedwagon.
 It features the lead guitar work of Gary Richrath.
 The song first appeared on REO Speedwagon's 1980 album "Hi Infidelity".
 It was the first REO Speedwagon single to break the top 50 on the U.S. "Billboard" Hot 100, reaching the number-one spot for one week in March 1981.
 The single was certified Platinum for U.S. sales of over one million copies.
 It peaked at number seven in the UK Singles Chart.
 "Keep On Loving You" has been described as "a mainstay on most '80s soft rock compilations" and has appeared on dozens of 'various artists' compilation albums, as well as several REO Speedwagon greatest hits albums.
You Can Tune a Piano, but You Can't Tuna Fish is the seventh studio album by REO Speedwagon, released in 1978.
 It was their first album to be co-produced by lead singer Kevin Cronin and lead guitarist Gary Richrath.
 The album was REO's first to make the Top 40, peaking at No. 29.
 The album sold over 2 million copies in the US, which led it to being certified 2× Platinum.
"I Needed to Fall" is a song written by Kevin Cronin and performed by REO Speedwagon for their 2007 album, "Find Your Own Way Home".
 The song was released as the first single from the album, and charted on the Adult Contemporary chart at #25.