Audacity is a free program that allows you to record and edit music. By default, the program contains a simple layout designed for the most fundamental recording and mixing jobs, but you can turn Audacity into a more powerful production tool by installing VSTs (Virtual Studio Technology) -- digital audio plugins that expand your range of capabilities.
Not all VSTs will work with Audacity. From the Internet, you can download and install VSTs for instrument effects, voice effects and most types of waveform manipulation. Audacity does not, however, support MIDI notation (as of May 2011), so you will not have the ability to use VSTs for virtual instruments and software synthesizers. Be sure to read the VST's description before downloading; if the word "MIDI" appears anywhere in the description, you cannot use it with Audacity.
Before you can install any VSTs for use with Audacity, you must download the VST Enabler, an extension developed by the Audacity team. The VST Enabler is a software extension that automatically integrates your VST downloads into your Audacity project window. You can download it free from the Audacity website, after which you must install it on your computer. The VST Enabler is available for both Windows and Mac OS X.
After installing any VST file from the Internet, just drag the file into the "Plug-Ins" subfolder found in your "Audacity" folder. To find your "Audacity" folder in Windows, open your "Local Disk" or "C" drive and select "Program Files." To find your "Audacity" folder in Mac OS X, open your "Macintosh HD" folder and select "Applications."
Accessing Your VSTs
After placing your VST files in the "Plug-Ins" folder, you can immediately access them from Audacity. Just open Audacity and click "Effects" on your menu bar (at the very top of your screen). Scroll down to the bottom of the list, beneath your default effects, and you will see your installed VSTs. Click any VST's name to open its corresponding "Options" window from which you can select your VST settings and apply them to your audio project.