If you fancy having a bit of fun next time you use Skype then why not try out a voice-changing app? You'll be able to do all sorts of cool things, from prank-calling your pals as Darth Vader to faking a sore throat in order to get a day off work. There are a number of software tools around that can change your voice in Skype, and none of them are particularly difficult to use.

Skype Voice Changer is a free app that does exactly what its name suggests. Install the application on your PC, open up Skype and agree to the permission request. You'll then be presented with an effects panel that lets you alter your voice. There are a range of presets and you can tweak each of them using the sliders to change various aspects of the sound.

A more comprehensive and easier to use solution is MorphVOX Pro. The program has some really cool preset voices, including a demon, robot, woman, kid and even a dog! You can also apply background noises to your voice as you're talking, such as a shopping mall or a traffic jam (perfect for a call to your boss saying you'll be late for work). Another great thing about MorphVOX Pro is the 'Voice effects' section, where you can apply various filters to your dulcet tones, including nasal, growl, underwater and monotone. All of the presets can be customized using the 'Tweak Voice' control panel. The downside of MorphVOX Pro is that it costs $39.95, although you can try the program free for 30 days.

If you really want state-of-the-art then check out AV Voice Changer. This app is loaded with a multitude of options that let you really fine-tune your fake voice. There are lots of preset voices to make you sound young, old, sexy, patronizing, joyful or sarcastic. The program includes a 'Parady Mixer', which lets you sample celebrities voices before calling people up and pranking them. The tinkering you can do with AV Voice Changer is more akin to a professional audio production app, including a formant morpher (to alter acoustic resonance), voice equalizer and noise reduction settings. The only trouble with AV Voice Changer is the trial is pretty limited, and the program is more expensive than MorphVOX Pro.

If you really want an idea of the fun you can have with voice changers, then you must watch this video of a guy using MorphVOX Pro with some hilarious consequences.