This project avoided the mistake of attempting to find impersonators for the characters portrayed, but appears to have succeeded in capturing their spirits. Joaquin Phoenix has a deep voice that in some ways echoes Johnny Cash, but is clearly not Johnny Cash. Nashville-born Reese Witherspoon was also a fantastic choice to sing June Carter's parts. There are other singer-actors here too, although none of them have enough opportunity here to convince me either way regarding their potential as singers. Their characters include Elvis Presley and Jerry Lee Lewis.
Some of the songs will be familiar to fans of the original artists but this is a soundtrack, not a greatest hits compilation, so the songs were chosen for their relevance to the script. Still, with Ring of fire, I walk the line, Folsom prison blues, It ain't me babe and Jackson among the tracks, there is no doubt who inspired the soundtrack and movie. Not having seen the movie, I don't know how accurately it portrays the Johnny Cash story, but the soundtrack is excellent.
While Joaquin Phoenix and Reese Witherspoon are no doubt content in their preferred profession of acting, I would certainly considering buying an album by either of them, should they choose to record one.