The instrument named alongside piano in the original song’s instrumental is the saxophone.
“Rein Me In” first appeared as a solo Sam Fender track on his 2025 album People Watching. Its arrangement was described as jazzy, with piano and saxophone providing important parts of the instrumental texture. The Olivia Dean version later turned the song into a duet, but the instrumental description refers to the original recording.
The saxophone is a woodwind instrument made of metal and played with a single reed, which helps explain its warm, expressive tone. It is often associated with jazz, although saxophones are also common in pop, rock, soul and classical music. The piano, by contrast, is a keyboard instrument whose strings are struck by hammers.
A common mix-up is confusing the saxophone with the trumpet because both are prominent jazz and popular-music instruments. The song’s description specifically names saxophone, not trumpet, harmonica or violin.