Looking for a stronger lead vocalist, Journey briefly enlisted Robert Fleischman and even recorded a few tracks with him, one of which, "For You", later appeared on the Time3 compilation album and Fleischman's solo album Perfect Stranger. Fleischman was soon replaced by Steve Perry, due to musical and management differences. Fleischman would later resurface as the first singer of the glam metal band Vinnie Vincent Invasion.
In "Feeling That Way", Perry dueted with keyboardist Gregg Rolie, who sings lead vocals on "Anytime".
"Patiently" was the first song Perry and Neal Schon wrote together. Perry wrote the lyrics, in which he expresses the sadness of being on the road and away from home, while also expressing admiration for the band's fans, and Schon wrote the music for the song. Other popular singles included "Lights" and "Wheel in the Sky". The latter was co-written with temporary frontman Fleischman.
Journey's manager, Herbie Herbert, enlisted English producer Roy Thomas Baker to engineer Infinity. Baker produced a layered sound approach, similar to his work with Queen, as demonstrated on tracks such as "Winds of March". In addition, Baker's method of stacked harmonies, notable on several other albums he produced, became trademarks of Journey's sound. He achieved this by having each vocalist (usually Perry and Rolie, sometimes joined by Valory and/or Schon) sing each harmony part in unison. This had the effect of making three or four voices sound like more, and is notable on the songs "Feeling that Way" and "Anytime", which are often played in tandem consecutively on radio stations as presented on the album.
The addition of Perry gave the band a more mainstream sound, and helped Journey attain their highest chart success to date.