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What are
Software Plugins?

Making sense of the VSTi, DXi, MAS, RTAS, and AU Jungle

By Rich the Tweakmeister

FXpansion BFD Drum Instrument VST/RTAS/AU (Macintosh and Windows)  Tweak: BFD is a completely
configurable drum kit that resides totally in software.

For Anyone who built a studio in the late 90's or earlier, its like being in a strange new world these days.  New, previously unreal possibilities are everywhere as the day of the Software Studio has finally arrived. It's here.  It's real. And it sounds excellent.  More and more, my studio is getting smaller.  I realize, as I look at the several tiered racks of equipment surrounding me that I no longer need any of it to make music at the quality I am used to.  I can do it all on my computer with my audio interface and monitors if I want to. 

There are 3 basic software devices that work in the software realm of the digital audio sequencer.  They are: Soft Synths, Soft Samplers and Software Processors.  This article chats about all three in general to get you grounded.  Then we'll devote a class on each of them specifically.  We'll also talk about Rewire applications here as they often contain softsynths, samplers and processors.

All 3 of these categories are sometimes referred to as "plugins".  They are called that because these are little computer applications that run inside a "host" application, i.e., a sequencer, typically.  These plugin devices are very important, as they have led the software revolution towards our virtual studios which is changing all recording studios, both home and pro.  Today there are few hardware devices left that cannot be emulated by plugins and software.  As you see from this page, software based synthesizers, effects processors, samplers and multi-track recorders can all work together on one single computer. 

But how well can these devices work together?  Aha! You are thinking!  Good!  That is a matter of utmost critical importance.  There's a lot of toys in the toybox, but a lot of them will not play well together, if at all.  Ok, now remember this: Bad Plugins Crash Sequencers. This is one reason to avoid free plugins.  I have used nearly every sequencer out there and can affirm that over half the reasons for instable, flaky operations is due to a poorly written plugins. You really have to be careful.  If you are having stability problems with any sequencer always check the soundcard driver and the plugins installed.  Even expensive plugins are often released full of bugs and fixed "eventually" as users complain.  Never trust stuff that was released last week or stuff that has not had an update in a few years. Plugins typically break when upgraded operating systems are released.  So keep an eye on these things and talk to actual users that use your platform and sequencer and get their take on stability. 

But I digress; let's get back to the topic.  Each sequencer has its favored protocol, and may refuse to work with the rest.  Cubase Sonar, Logic, Pro Tools LE and Digital Performer all want plugins to follow defined rules, which we will call plugin formats.

Plugin Formats

Here it is plain and simple. 

VSTi (virtual studio technology instrument) was developed by Steinberg as a Universal platform for soft synths and samplers.   Not all the companies bought into it. Cubase and Nuendo use it extensively.  You may also hear about VST2 and VSTi2 plugins.  VST2 is simply an extension of the VST format. These pass on more parameters to the host for automation.

Are PC VSTs and VSTi compatible on Macs?  Always assume the answer is no unless the developer makes it clear. If they made a Mac version, they will be sure to list that.  Usually, developers will have a PC VSTi version and a Mac VSTi version, so be careful to get (and install) the right one. Usually, these days they are both on the same cd rom. 

DXi: Cakewalk, initially, did not go with VSTi, it went with DXi, which is based on Microsoft direct X code.  Today, however, they have relented an allow use of VSTis with Sonar in a shell.   DXi's cannot be run on Macs.  By the way, Steinberg has dropped DX plugins in Cubase.  Its going away.  I personally will not be getting any more DX or DXi plugins.

Ok by now you may be wondering what this "i" business is.  You see VST, then VSTi, then DX and DXi.  The "i" stands for "instrument", like a softsynth or sampler to distinguish it from a plugin processor, like a compressor, reverb or delay. 

AU, short for Audio Units, refers to a format developed by Apple for Mac OS 10.x  Because there is support in Apple's operating system, AU is used by many Mac sequencers and audio applications, and is the major supported format in LogicPro.

Important note: Just because Logic favors AU does not mean it will run all Audio Unit Plugins. As of Logic 7, Apple got stricter.  Logic only supports AUs that follow Apple's guidelines and not all of them do.  This is Apple's way of forcing plugin developers to follow the rules it developed.  Its a good thing, as the Audio Units that do pass are less likely to crash Logic. 

MAS refers to plugins that work with the MOTU Audio System in Digital Performer (Mac only), which can also use VSTi, AU and ReWire.  You'll note that fewer plugins support MAS, and that's because MOTU DP users can use AU as well as MAS.

RTAS is the format used by Digidesign, the maker of Pro Tools LE, which comes bundled with the popular Digi 002 interface. RTAS will also work in Pro Tools M-Powered, which works with M-audio interfaces.  RTAS plugins, however, will not work in Logic, Cubase or Sonar.   

Audiosuite is another Digidesign format which works with the above software packages and hardware interfaces.

Rewire, finally, is a scheme that pipes digital audio from Reason and Rebirth, Project 5 and Ableton's Live to other sequencers.  It basically allows you to run a sequencer inside of a another sequencer.  Its not a plugin per se, but because many soft synths use Rewire I include it here.

Q) What is a Plugin Wrapper

A) A plugin wrapper usually refers to a software device that fools a host (i.e., the sequencer) into using formats that would be incompatible without it.  For example, in a VSTi to DXi shell you can run VSTis and the sequencer will treat them as DXis.  Through the use of wrappers, Sonar users can use VSTis and Logic Users can use VSTis.  Without a wrapper, Logic can only use AUs and Sonar (up to version 4) can only use DXis and Pro Tools LE not use VSTs. 

There are some disadvantages to using wrappers.  If the wrapper does not convert and pass on the data perfectly, there could be problems.  Remember: Bad plugins crash sequencers.  Right?  Right!

Software Synths

A Soft Synth mimics a hardware synthesizer with different sounds and waveforms.  Many follow the model of a vintage analog synth with oscillators, filters, lfos and amp envelopes making the sound, other's may use a model of FM, wavetable, or may be modeled after an acoustic instrument.

Are Soft Synths Better than Hardware synths?


Well, you will never break your back carrying a soft synth to a gig.  But softsynths will rather quickly degrade your PC's performance as they eat CPU cycles with veracity.  Why is this? The CPU must deal with the soft synths instructions immediately or there will be latency.  Most fast computers can achieve a latency of 5 milliseconds and when they do, the soft synth "feels" like a hardware synth when you play it.  However, as you build your song and have 10-16 softsynths playing back at this incredible rate, the CPU gets behind in other tasks.  When you add effects on top   might notice clicks and pops and other nasties in your audio.  If you don't heed the warning, suddenly the whole shebang may stop dead in its tracks.

Hardware synths do not suffer this as it just has to receive midi data on time, which is any computer can do easily.  So you can use your CPU for other tasks, like recording audio, effects, even running other applications. 

Soft synths are as good sounding as many hardware synths, sometimes better. They also can be very specific in their focus.  People don't mind spending $350 for a softsynth that just does pads and atmospheres, but they would mind buying a hardware box that only does this for $2000.  Hardware costs more because making the thing costs more.  Once software is made it is much less of a problem to make 100,000 units.

Here's the page where we talk about software synths in greater detail.

Soft Samplers

What is the difference between a soft synth and a soft sampler?

A software sampler works like a digital sampler.  These don't sample sounds per se (you usually need an audio editor/recorder for that). But they do take "samples" (i.e., .wav or .aif files typically) and let you map them along your keyboard, the same way one does in a hardware sampler.  A soft sampler may let you load sample cd roms that are used by hardware samplers which gives you access to a universe of premium sounds.  Once you map the samples to the keyboard, you can then program them with filters, lfos, amps like a soft synth.  One advantage of soft samplers over their hardware rivals is that there is no memory limit to how many samples are immediately accessible--any wave file on the computer is fair game.  Compare that to hardware samplers that have banks which are limited to 128, 256, or maybe 512 megabytes.

So the soft sampler has an open architecture which lets you import any sound.  The soft synth is a closed architecture that allows you to select from a number of supplies internal waveforms.  You can read more about soft samplers on the next page in this series

Software Processors

Its perhaps with plugin processors that the home studio operator gets a shot at being a mixdown and mastering engineer.  This is a fact that has not gone unnoticed by true professional audio engineer, many of whom are quite rightfully irritated at the bloody hoardes of noobs that try to wrestle the secrets of mastering out of them.  As I have said many times, these skills come from knowledge and experience.  So get some.  No!  don't ask people on the forums "whas da beh compres..settin for my beatz" To gain knowledge and experience you sit there with the machines (virtual or real) and experiment over and over again.  Then you start seeing patterns and hearing results.

The mindblowing thing is that many of the processors that studio engineers have used now have software equivalents.  These plugins are sometimes so good the the mastering engineers themselves use them! 

As you might expect the professional plugins are not cheap, but they are a lot cheaper than the roomful of gear one used to have. 

So are you ready to dive into plugin processors?  Here's the page.

Rewire Applications

Rewire came from the propellerheads, the developers that brought us Rebirth and Reason which are both a combination of a software synth and a sequencer.  Rewire is not a synth or a plugin; its a method by which 2 sequencers can pass digital audio from a "slave" sequencer to a "master" sequencer. 

Basically, the rewire slave routes the streams of digital audio through channels that connect the two applications together.  I view it as a series of pipes from one application to the next.  The audio goes out the pipes and ends up in the Master Sequencer's virtual mixer.  Once in the master sequencer, you can add plugins and process the signal before you direct it to the soundcard, audio interface, or output it as a file. 

The Propellerheads have a massive virtual application called Reason  Reason is like a total software studio in itself with one exception:  It does not record audio. Hence we need Rewire so we can run Reason inside an application that does record audio. Make sense?  Cool!

Reason's look is totally awesome. You can turn the rack of synths, drumboxs, effects around and mess with patching cables, doing some very advanced tweaks, like routing control voltages from the synth to modulate parameters in other instruments--hehe, exactly the kind of tweaking many trance artists used. Except in Reason, you do it on the screen, instead of crawling behind a 8 foot rack of gear with a flashlight If you like to tweak synths, you have to try it.  Reason records all your knob/fader moves, and you can do incredibly nasty things to drum loops, samples, midi sequences.   

If you use Rebirth, you'll  love Reason and you can run Rebirth from within Reason and route the outputs through the Reason Mixer and FX.  The most outstanding bit with Reason, IMHO, is the killer sound.  If you want to put some real hipness into your mix, this is it.  Reason is an efficient running program and you can get dense mixes on an average computer.  The program exports to WAV very nicely so you can use other applications to add vocals, master, and further tweak. I have it, and will attest to its intense sound.

If you like classic Techno music, Propellerhead's Rebirth is a must have.  It is the classic 808/909/303 all in one program and it sounds utterly authentic.  Knobs and sliders function in real time just like on the original machines and you can watch all your tweaks on playback.  Why mess with loops when you can get awesome results with Rebirth and totally control every note?  If you are serious, you have to have it in your virtual toolbox. Add a bit of delay to the outputs and you are transported to realms that are very psychedelic, grubbing around in a vast techno feeding ground.

Unfortunately, Rebirth has not had an update in a long time.  It won't work on Mac OS X at all, but will still work on PCs and in Mac OS9

The third Rewire Application is the Ableton Live.  I wrote a review of it elsewhere, so go check it out.  The Ableton Live hooks into your sequencer's mixer and pipes in hit fresh audio loops, perfectly timed to the sequencer's BPM, with it's own killer FX engine. 

A more recent addition to the list of Rewire applications is Cakewalk's Project 5.  It needs a powerful computer, but if you have that, it can really make your rig move with hot electronica and effects.  See my review.


Q) Can you run more than one Rewire application in a sequencer? 

A) Yep! If your CPU is up to the task.  Perhaps the biggest drawback to Rewire is that it takes a lot of CPU to run 2 real-time recording applications on a single computer.  However, I have at times run Reason and the Ableton live under Logic on my G5 and while I would not want to do this every day it does work. 

To Sum Up

OK, this was a tough class.  The subject matter can be confusing as plugin makers don't tell you everything I told you here.  They leave it up to you to figure it all out.  The virtual studio indeed is an amazing phenomena of our age. Its a virtual paradise of musical possibility!  But like all things on earth, there is trouble in this paradise, mainly for those who don't pay attention to many of the issues raised here..  I hope I have helped you get a solid handle on them so you can enjoy the benefits and sidestep the problems.  May you enjoy your virtual universe of sounds and use your power for good.  



Rich the TweakMeister

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