One of Katy’s party guests looked surprised at my outdoor stereo setup.

“How?” he asked me.

He pointed at the iBook laptop computer sitting on a desk inside the house, which had iTunes running.

Then he pointed his other hand out to the stereo that was booming music from the laptop to the guests across the back yard.

“How are you doing that?” he asked again, his outstretched arms still pointing both ways, only now adding a shrug of disbelief. “How are they connected?”

Several other curious eyes from my daughter’s party fell on me. Their voices became quiet.

I felt like David Copperfield, without the smoke and mirrors.

“Magic,” I said, getting some laughs.

Wireless magic

I took him outside and revealed my secret.

In the electrical outlet on the back of the stereo receiver, I had plugged an Apple AirPort Express, a small white box about the size of a pack of magician’s playing cards.

The AirPort Express is a small, portable 802.11g wireless networking device I recently bought for my home computer network.

Plug an ethernet cord into it, and it will serve as a wireless network to the Internet or as a bridge between computers. Plug in the USB cord from your printer, and you can print wirelessly from any computer on the network.

There’s one more rabbit you can pull out of the hat – it lets you wirelessly play the music on your PC or laptop to your stereo.

I showed Katy’s party guest that all I had done was plug an audio cable from my stereo into the AirPort Express.

Then, all I had to do was go into iTunes and bring up the song I wanted. Without even having to say Abra-Mac-Dabra, I could connect through AirTunes, which is part of the iTunes software.

Presto! I could choose where I wanted the sound to play.

Once I picked the network – in this case, the stereo in the backyard – I could use my laptop like a digital jukebox, either playing songs I had on iTunes, accessing an Internet radio station or popping in a CD to play.

Doing Windows

You don’t need a Mac to use the AirPort Express, iTunes and AirTunes – the iTunes software also is available as a download for Windows 2000 or later operating systems.

The cost for the AirPort Express is relatively cheap, about $129, then a few dollars for the audio cable.

I called Marcus Brannon, a techie over at Best Buy, and asked what other wireless solutions could connect a computer to a stereo. The AirPort is probably the easiest all-around solution, he said.

But he found a few other options.

One is the Linksys WMB54G Wireless-G Music Bridge, which runs about $100. It is supposed to be able to play any sound coming out of your computer – even the e-mail alarms – through your stereo, boombox or home theater speakers. It also has a remote.

The reviews I found on it said the hardware was easy to connect to the stereo, but some people found problems in getting the software to connect wirelessly.

Another product the reviewers liked was the Logitech Wireless Music System for PC, which runs about $150.

Brannon also mentioned the Roku Soundbridge ($199), which includes software for either a Mac or a PC, as another option.

Disappearing act

The party was over. I had lugged my old heavy stereo speakers back indoors and left them and the receiver in the family room.

The next day, I started looking for a spot where I could set them up inside the living room or the family room.

“When are you going to get those things out of here?” my wife asked.

I told her I wanted to start using them again, because of the cool wireless wizardry.

A few minutes later, I was lugging the boxy speakers back downstairs.

My wife hadn’t said a word, but there certainly was some wireless communication happening.

It was almost like . . . magic.