The Decepticons are constructing engines on a comet, which Galvatron plans to crash into Metroplex. But a group of Autobots find the comet and a battle begins. The Decepticons eventually retreat, but the comet's new engines are activated. The Autobots attempt to stop the comet by shooting it, but then the Decepticons come back and attack them. However, they're then all hit by waves of sound energy, which result in the comet being destroyed, whilst the Transformers crash land on Eurythma, the planet the sound came from. They resume fighting there, but Galvatron and Soundwave head off to find the source of the harmony -Galvatron wants to use its destructive powers. Ultra Magnus sees them leave, so he, Broadside and Blaster head off to a nearby city.

The Autobots arrive first. They meet Basso Profundo and explain to him about the dangers of the Decepticons, but he refuses to help them, believing his sound energy to be enough to protect the city. Magnus asks if everyone in the city feels that way, but Basso says anyone who doesn't can leave, like Allegra, another resident of the city he's fallen out with recently. Galvatron and Soundwave are nearby and overhear everything, and head off to find Allegra. The Autobots search for Allegra, but Galvatron blasts a bridge and causes the wreckage to fall on them. They are saved by Zebop Skandana, who is one of the three who sang the harmony earlier -with Basso and Allegra being the other two. Meanwhile, Galvatron and Soundwave get to Allegra first, and know of her falling out with Basso. Galvatron says he'll help her overthrow Basso, if she gives them her part of the harmony. She agrees, and Soundwave records it.

The Autobots head to where Allegra is, but Soundwave attacks them with his new musical weapon. The Autobots are repelled, so Zebop sings his part of the harmony to try and help. Soundwave records this too, as the Autobots and Decepticons resume their battle. Blaster and Soundwave accidentally fall on top of Zebop. As the Decepticons retreat, Allegra has realized the Decepticons are bad. She uses her musical harmony to heal Zebop.

The Decepticons regroup and resume attacking the other Autobots. Basso sees this and tries to stop them with his harmony, but is unsuccessful. Soundwave also records it, meaning he now has the complete harmony recorded. The Decepticons leave the planet and head to Earth, so they can use the harmony against Metroplex. The Autobots head into the city, and Basso blames them for everything that has happened. Blaster blames him for trying to trying to run it all. Basso and the others heal the Autobots, and then they all head to Earth. At Earth, the Decepticons arrive and Soundwave plays the harmony, which is able to stop Metroplex in his tracks.

The Autobots then arrive, and Basso, Zebop and Allegra sing their harmonies together. The power of this is greater than Soundwave's recording of it. Blaster then fights Soundwave and is able to erase his tapes, resulting in him losing his recording of the combined harmony. The Decepticons retreat, whilst the Autobots take Basso and the others back to Eurythma, where Ultra Magnus tells them they've got to learn to live with each others' differences, if they are going to live in harmony. As they put their hands together, Blaster says that's the name of that tune.

Notes

-The Secret Files segment for this episode is about the Quintessons.

-This is the most poorly animated episode of The Transformers. It's widely believe it was animated by AKOM, but they clearly had the Z team working on this episode, as it looks far worse than anything else they've done for the series. Many of the errors just stand out so much, such as characters being the wrong sizes, members of the special teams being on screen at the same time as their combined forms etc.

-The combiners aren't treated very well in this episode. Perceptor shoots Devastator once and destroys him (and I mean that -he gets blow to smithereens, but the Constructicons are all alive and well a couple of shots later) and then later on, Superion gets blown back into the Aerialbots by a single laser blast.

-Finally, if there's one good thing to say about the animation, it's that this episode has a very rare appearance of Metroplex's vehicle mode, which is something that he almost never uses within an episode itself -he's usually always in either his robot or city modes.

Errors

-When Soundwave says his "is that wise" line to Galvatron, his mouth doesn't move.
-Devastator is the same size as Soundwave during this shot. The Constructions are then seen forming Devastator a few seconds later.
-The most infamous part of the episode is this shot, showing Brawn and Huffer firing at the engines. Brawn died in the movie, whilst Huffer was confirmed as dead in Dark Awakening. Bonecrusher is also shooting at the engines, despite being a Decepticon.
-Hook and Scrapper are tiny when Magnus bashes them together.
-When Broadside complains about the dents on him, his eyes are colored yellow instead of blue.
-Soundwave has an Autobot insignia on his chest during this shot.
-Soundwave is way too small when Galvatron randomly picks him up.
-For some reason, Zebop has to hold on to one of Broadside's wings when they head to Allegra's place. Couldn't he sit in Broadside's cockpit instead?
-Soundwave's chest Decepticon insignia is missing during this shot.
-When Blaster says "Oh great, scorch marks on top of everything else!", Broadside's voice is heard.
-Hot Spot is suddenly with the Autobots when Soundwave plays the harmony back at them. He wasn't there earlier. It seems he was used instead of Broadside.
-Blaster has a Decepticon insignia on his chest when he picks Zebop up.
-Magnus mouths Blaster's "they used their harmonies for everything" line.
-Hot Spot is standing in front of Defensor during this shot.
-When Superion dives towards Galvatron, a space background is used, but the current scene is meant to be on Earth.
-Superion is also really small when he tackles Galvatron.
-Blaster overlaps Soundwave during this shot.