(The Box Tops had) “never been in a studio before ‘The Letter,’ but they knocked it out,” (Stereogum). “Producer Dan Penn added in a plane-taking-off noise that he’d pulled from a sound-effects record that he’d checked out of the library. Given all that, ‘The Letter’ should be a sloppy and amateurish record, which wouldn’t necessarily prevent it from being great. But ‘The Letter’ is not that. It’s a two-minute epic.”
Despite being not even 20 years old at the time, frontman Alex Chilton “sounds weary and ravaged. He’s stuck somewhere far away from his baby, and he’s got to go see her right away. We don’t know where he is, why he’s separated from her, or what she wrote in her letter … But Chilton’s voice absolutely pops off of the record, and it’s all the band needs to tell the story. ‘The Letter’ is a tight, hard, compact piece of white-kid soul. (It’s the last #1 song ever to come in under the two-minute mark.) But it sounds big and cinematic anyway, with Chilton’s voice fighting its way through nervous organs and melodramatic strings and horn stabs … There’s nothing lo-fi about the record; even if it was recorded on a low budget, it’s got the sweep of a James Bond theme.”
The track sticks to A minor for most of its length, but jumps up to C# major at 1:33 for its tiny instrumental outro. The horns have made their exit, leaving the strings to lead the fast fade-out.