Toot

The film then jumps to a group of four cavemen, each of whom have discovered the nuclear form of one of the above sounds. We begin with a portly Caveman Toot who has discovered that blowing through an old cow's horn produces a pleasing "toot". We advance to ancient Egypt in 2000 BC, where Caveman Toot discovers that metal horns produce even better sounds. He celebrates by breaking into a two-note jazz solo as Egyptian characters painted on the walls boogie down.

We return to Professor Owl, who explains that making a trumpet longer made its tone lower. We then visit a Roman trumpeter who crashes into a column and bends his horn into a grotesque shape—however, he soon discovers that despite this change in form, the trumpet does not sound any different: it is possible to change the horn's shape without changing the pitch.

However, as Professor Owl explains, this horn can only produce certain notes; in order to get all of the notes required for even a simple tune, you would need four horns of different lengths. But if we create a horn with valves, we can effectively have four horns in one, and this fact is celebrated with another solo.

Whistle

We return to the cavemen, where Caveman Whistle is trying to impress his "cave girl" by blowing through a tube of grass; he further discovers that adding holes to the tube allows him to modify the "whistle" in interesting ways—the more holes Whistle adds the longer the grass tube gets and he invents the first flute. The cave girl is impressed, but then a rival caveman appears, bonks the cave girl on the head with his club, and drags her off by the hair—which makes Caveman Whistle angry.

Professor Owl explains that this system of holes is the basis for every woodwind instrument, including the clarinet played by Johann Sebastian Bach and the saxophone played by a jazz musician.

Plunk

Caveman Plunk has discovered that plucking on the string of his bow produces a pleasant "plunk" sound. An off-screen choir explains–as the animation shows–how to create a simple harp from "taller" Caveman Plunk's bow by adding a jar to make a resonator, adding some extra strings, changing the jar to a box of wood, sliding it down and adding tuning pegs, and rearranging it all—and Plunk invents the first harp.

Professor Owl mentions that you can either pluck the harp, which played by a taller Caveman Plunk; or play it with a bow, which played by a shorter Caveman Plunk. We then briefly visit several periods in history, where we see several stringed instruments being played in similar fashion, and finish with a string quartet, and all of them ending with the strings being broken.

Boom

Caveman Boom hits his stomach to produce a "boom", and hits other things with his hand and his club to make other sounds. Professor Owl escorts us through history and explains how a variety of percussion instruments emerged from this basic theory, ranging from rattles to complex drum kits and even the bass drums of marching bands.

Conclusion

The chorus recaps that all music, from the trombone to the calliope to the banjo to Latin percussion to "music oriental" to an orchestra in a concert hall, emerge from the four core sounds with Caveman Toot in the brass section, Caveman Whistle in the woodwind section, Caveman Plunk in the string section and Caveman Boom in the percussion section, all wearing top hats.

Comparing CinemaScope and flat versions

Both CinemaScope and flat versions of Toot, Whistle, Plunk and Boom consider major changes for either television runs or theaters that were not equipped for CinemaScope.

• The most notable change comes at the transition from the end of the "Boom" section to the parade that starts the finale. In the CinemaScope version, the background and characters fade out, leaving the bass drum in the last scene alone; the bass drum then jumps from the side of the screen to the center, and the parade fades in. In the flat version, the camera zooms in on the bass drum, dissolving into the parade and zooms back out.
• Shots of multiple repeated characters (like the bird chorus at the end, for instance) were cut in half, using two repetitions instead of four.
• Some of the characters like the kitchen bird band members near the beginning and the string quartet members get closer together in the flat version. They were separate far enough in the CinemaScope version.
• In the flat version, Bach with his clarinet has a book of sheet music with "BACH" written on it instead of the busts around him in the CinemaScope version.
• In the flat version, Plunk morphs into the Egyptian playing the harp instead of fading out to him in the CinemaScope version.
• In the CinemaScope version, the grand piano also in the plunk segment stretches but in the flat version, it stays a certain size.
• In the CinemaScope version, the Caveman Whistle gag considers only one scene including a zoom-in. In the flat version, it was edited into multiple scenes. Some of these changes include zoomed in shots of the impressions. The only major change in the Caveman Whistle gag is the screen panning to the right to reveal the rival caveman hitting the cave girl with his stick.
• In the CinemaScope version, the shorter Caveman Plunk can be seen in the far top left during the creation of the harp. He doesn't appear until afterwards in the flat version.