To be catchy in a pop or commercial context, it needs to be simple and repetitive. Whether one is composing a song or a commercial jingle, simple and repetitive is mandatory.
It takes some unlearning, but the fact is, what we call "classical" music is catchy the same way as popular music. Think of the Beethoven's 5th motiv. Yeah, it's "serious" but it's catchy. He built the whole tune around it. So is the opening riff from Ghostbusters. Bach's minuet in G was catchy, too, and in a very similar way as pop music. The Air on a G String is that tune Procol Harum used for White Shade of Pale. Catchy.
Pachelbel's Canon is as close to popular music gets, its in the eye of the beholder. Fact is, it wasn't all that popular in its day. But it was the repetition, just like many popular songs, that was catchy. He was a working musician, a church organist, and he came up with a catchy tune for the frickin' ages. Always remember that these were real people just trying to get by and feed their "public" (usually some royal patron) what they wanted to hear.
The Spanish musical group Ensemble Hesperion has spent the last 40 years or so showing snooty Early Music types that Spanish and other court musicians jammed just like modern ones do. They had a few super catchy tunes, like the Chacona and Marizapalos. They were super popular in their day and delighted people. The manuscripts that were left from those days are basically lead sheets with the most memorable and catchy variations scribbled down. Confident musicians who understand the style can them improvise on top of them. It's pretty cool.
This is the Ciacona. It's catchy like rock music yet hails from the 17th century. It's a through-composed piece for four or five voices, but the instrumentalists can play around. The lyrics are filthy, they are about a drunken all-night party where everybody is screwing, but the chorus keeps reminding everyone to keep dancing the darky dance from the Canary Islands (not kidding, the Chacona was attributed to the mixed culture of slaves, free Africans and expelled Spaniards who lived there). And the little Baroque guitars are wailing away...The first time I heard this tune was almost 40 years ago, and my mind was bent at how catchy it was yet it was "classical" music. This group has been doing this song for all this time.....
https://www.youtube.com/watch?v=LcgzDveou2c
It's the imprint of "serious" music that is what blinds people from realizing the commonality of being catchy and that you don't need to put on a suit to listen and enjoy certain kinds of music.
