Duo is an acoustic album by Richard Marx and Vertical Horizon vocalist Matt Scannell. The disc was released on May 12, 2008, exclusively through RichardMarx.com and was later made available for sale at their concerts together as well. Marx and Scannell exhibit both of their acclaimed works. Marx remade a version of "Always On Your Mind," for his 2008 album Sundown. The disc is predominantly done on acoustic guitar aside from the track "Give You Back" performed on piano.
- Richard Marx – lead and background vocals, acoustic guitar, piano, producer, arranger
- Matt Scannell – lead and background vocals, acoustic guitar, producer, arranger
- Joel Numa – engineer
- Mat Prock – engineer