Musically, "(Sittin' On) The Dock of the Bay" was a departure for Otis Redding. An established R&B star, Redding had set out to create a song with cross-market appeal when he recorded his famous 1967 hit. It was not a narrowly commercial decision. Redding was buoyed by his success in reaching a wider audience at the Monterey Pop Festival, and he was intrigued by The Beatles' recently released Sgt. Pepper's Lonely Hearts Club Band.
The evolution in Redding's style is immediately apparent in this song. At the beginning, the only sound rising above the ocean waves is Steve Cropper's acoustic guitar, which fills an almost folk-like rhythm role. The bass guitar that also enters early is equally reserved, providing just enough force to move the song forward, but not enough to break the wave-echoing, rhythmic feel of the song.
The spare feel of the song was about more than just pace—after all, Redding had sung plenty of slower songs. But in others, he had used more instruments to build a layered, complex sound, as with the fanfare-blowing horns in "I've Been Loving You too Long" and "A Change is Gonna Come," and the piano and electric guitar in "These Arms of Mine."
What's not surprising about "Dock of the Bay" is the emotional strength of Redding's vocals. Booker T. Jones (a member of the Stax Records house band and later leader of Booker T. and the MGs) emphasized that Redding did not bring unusual range to his singing: "He had no really low notes and no really high notes," Jones explains. But what he had was emotional power. "Otis would do anything that implied emotion, and that's where his physicality came in, because he was such a strong, powerful man."
Oh, and about that whistling – the story goes that Redding had just whistled as a placeholder for another, unfinished verse, which he never had time to complete. Even if he planned to eventually cut the whistling out, we think it actually works great with the sit-and-watch-the-waves feel of the song.