It's 3am, and sleep is playing hard to get. I should be dreaming and snoring, but instead I'm lying on my back and listening to the house creaking while the curtains billow slightly against the draughty window.

The worst thing about being unable to sleep? The music, or bits of half remembered song that rattle around in my mind. Last night I had one miniscule section of that Tinie Tempah single running on an endless loop in my skull - in particular, the part where he raps about having so many clothes that he has to keep them at his aunt's house. It's a horribly infectious tune, with a lo-fi hookline running in the back ground that sounds like a malfunctioning Game Boy. Those lyrics, meanwhile, present a maddening enigma: if Tinie's wealthy enough to own so many items of clothing, why doesn't he simply buy a bigger wardrobe? And how does his aunt feel about having her nephew's clothes cluttering up her bedroom?

"Look, Tinie," she'd say. "I know I'm your aunt and everything, but you can't just keep coming around here with bags full of clothing. Look, here's a fiver. Put it towards a new wardrobe."

And besides, if your home's storage space was so limited that you had to keep some of your jeans around your Auntie Flo's flat, would you really want to tell people about it in your next single? These are the questions that plague me during long sleepless nights.

Anyway, Tinie Tempah was so last night. This morning's insomnia soundtrack is the theme tune from Picross 3D for Nintendo DS, which sounds like the kind of music you'd hear playing at a fairground owned by the Devil; an endless, bouncy jingling waltz of false frivolity. And it's buried in my brain like a warbling bullet, playing over and over again. It's the kind of tune I find myself humming the following day as I shuffle about, grey faced and scarlet eyed.

It's the electronic, bleepy theme tunes that are the most catchy. Think of Tetris' iron curtain ditty, or perhaps the theme tune from Taito's forgotten antipodean platformer New Zealand Story, a relentlessly chirpy number that sounds like the work of a grinning lunatic let loose on a Casio keyboard.

A theme tune's hypnotic powers appear to dissipate as it becomes more sophisticated. Compare the simplistic chirps and peeps of the original Super Mario Bros theme on the NES to the 21st century soundtrack running throughout Super Mario Galaxy; as memorable as Galaxy's soaring, sumptuous John Williams-like orchestral music is, it's the NES version's single channel calypso warble that, once heard, remains buried in some ancient synapse in the brain and refuses to come out.

Similarly, compare the original Legend Of Zelda theme with that of its modern counterpart, Twilight Princess: one sounds evocative and cinematic; the other will haunt you for months.

That's not to say that modern game music isn't catchy, however. EA's freebie online shooter Battlefield Heroes contains an opening melody that is derived from the same musical DNA as whistle-along marching tunes like Hitler Has Only Got One Ball or I Was Kaiser Bill's Batman, and it is surely one of the most annoyingly memorable themes in recent years.

But, like the themes found in Picross 3D, ancient classics like Super Mario Bros or Zelda, or even Tinie Tempah's hit single about a surfeit of clothing, it's the simplicity of the Battlefield Heroes melody that makes it linger in the mind like a noisy and unwanted squatter.

And this is the secret to writing a truly infectious videogame theme tune, I've decided: compose it on the tiniest, simplest keyboard you can find at a car boot sale (preferably the kind with a dozen keys and a demonstration button), use only a handful of notes, and play those same five or so notes repeatedly, over and over again. These are the kind of theme tunes that come bubbling up from the depths of my subconscious at 3am as I mull over life's deepest philosophical mysteries: death, the existence of God, and the clothing arrangements of rappers from South East London. 

Ryan writes his gaming column every week at Den Of Geek. Last week's is here.