If you're working inside a digital audio workstation (DAW) and you want some nice reverb, or maybe a compressor or two, you're going to need a plug-in. A plug-in is the software equivalent of a hardware effects processor. Depending on what recording software you opt to run, you might need different types of plug-ins. Each recording program requires plug-ins to be written in a specific language that the host program will understand. Luckily, most plug-in manufacturers include multiple versions when you purchase, but not all. Let's break down all the major formats so you can see what's around.

VST

VST (virtual studio technology) is a plug-in standard format created by Steinberg, which also makes Cubase and Nuendo recording software. VST plug-ins work not only in Cubase, but other programs have adopted the use of VST plug-ins. VST plug-ins are available for both Macs and PCs. Because VST has been around for a long time, there is a nice selection of VST plug-ins available.

RTAS

RTAS (real-time audio suite) is the only plug-in format that works inside Pro Tools. Because of the widespread use of Pro Tools systems, there are many RTAS plug-ins available on the market. Because Pro Tools runs on PCs and Macs, you can find RTAS for both. The British company FXpansion has created a VST to RTAS converter allowing the substantial amounts of VST plug-ins to be utilized inside Pro Tools.

DirectX

DirectX is a Windows-only plug-in format that is used by Sonar and other popular Windows audio programs. DirectX was originally a multimedia language introduced by Microsoft to write games and other multimedia programs. Because of its integration into the Windows operating system, DirectX is used by many of the Windows audio programs. Sorry Mac people, Windows only!

Audio Unit

Audio Unit is a new type of plug-in format introduced by Apple as part of its remake of the Mac operating system version 10 (also known as OSX). The thought behind Audio Units was to create a system-level plug-in format that worked inside the operating system and could be available to any audio program on the system. Unfortunately, the only two major software makers using Audio Units are Logic and Digital Performer. Other programs use Audio Unit plug-ins on the Mac platform — Logic and Digital Performer are the major software platforms that do. Apples free recording software “Garage Band” utilizes Audio Unit plug-ins as well. This might change because the Audio Unit is in its infancy on the Mac platform. Audio Unit plug-ins are available only on the Mac platform in OSX or higher.

MAS

MAS (MOTU audio system) is the plug-in standard written by MOTU for use in its Digital Performer application. Before Version 4 of Digital Performer, MAS was the only plug-in that could be used in Digital Performer; however, now Digital Performer uses MAS and Audio Units. Since Digital Performer is Mac only, no Windows versions of MAS plug-ins exist.

Wrappers

A wrapper is a program that converts plug-ins from one type to another type. On the PC side there are DirectX-to-VST wrappers that extend the choices of Windows plug-ins. One the Mac side there is a VST-to-Audio Unit wrapper that greatly improved the number of available plug-ins while OSX was just starting out; however, developers have been slow to write Audio Unit versions of their plug-ins. That is getting better over time as Mac OSX continues to evolve.