The time has arrived. With a reasonably powerful laptop computer andan affordable collection of software instruments, you can easily takeyour studio on the road. And with suitable MIDI controllers and anaudio interface, you can even take your portable studio onstage.

Software synthesizers come in a confusing array of formats, but theyhave a lot in common under the hood. In this column, I'll cover thebasic things you'll need to know when choosing and using a softwareinstrument. I'll also point out some important features and certainpotential trouble spots that you should be aware of as you assembleyour system.

TO PLUG OR NOT TO PLUG

Software instruments come in two types: standalone and plug-in.Standalone instruments are excellent — perhaps even preferable— for live performance. That's because they take complete controlof the interaction with the drivers for your MIDI and audio interfaces,and this often results in lower latency. Plug-in instruments are oftena better choice for desktop composition because they don't requireintermediary software (such as Propellerhead's ReWire) forcommunication with your digital audio sequencer. It's not uncommon fora software instrument to come in both types, and in some cases theplug-in simply provides input and output to the standaloneinstrument.

Some plug-ins are native, which means they rely on the computer'sprocessor for their operation; others require separate DSP hardware.Examples of the latter include Digidesign's TDM systems, TCElectronic's PowerCore, Creamware's Pulsar, or Mackie's Universal AudioDevice (UAD). I'll concentrate on native formats here, but many of thesame considerations apply to proprietary systems.

Native plug-ins come in several formats, but from a practicalstandpoint, your choices are limited by which host software you use(see the table “Plug-In Instrument Support”). Perhaps thebest-known plug-in format is Steinberg's Virtual Studio Technologyinstrument (VSTi), which is supported by a number of hosts. On the PC,the other main choice is Microsoft's DirectX instrument (DXi), which isused by Cakewalk's Sonar among others. Some PC hosts support bothformats. On the Mac side, in addition to VSTi, you'll encounter Mark ofthe Unicorn's MOTU Audio System (MAS), Digidesign's Real Time AudioSuite (RTAS), and for OS X users, Apple's Audio Units (AU). BecauseMOTU now supports Audio Units, MAS will probably fade away as OS Xtakes over the Mac world.

RACK 'EM UP

The first task in using a software-instrument plug-in is to get itinstalled and accessible to the desired host. That business is usuallyhandled automatically by an installer that is supplied with theplug-in. It's important, however, to know where the installer puts theplug-in. VSTi and DXi plug-ins are typically placed in a folder in thesame directory as the host application, and you can often sidestep asecond installation for a different host by copying the plug-in to anew location. MOTU Digital Performer and Digidesign Pro Tools plug-insreside in folders inside the System's Extensions folder. In Mac OS X,all plug-ins live in shared library folders where they are accessibleto all of the appropriate hosts.

FIG. 1: In Steinberg's Cubase SX,software instruments are inserted into a virtual VST instrument rack(top right). The instrument's control panel can be opened for editing(center), and the instrument's output appears at a channel strip inCubase's Mixer (lower left). MIDI for playing and automating isdirected to the instrument through a MIDI track (topleft).

Software instruments are handled differently by different hosts.Some hosts (Steinberg Cubase SX and Cakewalk Sonar XL, for example)have an instrument rack into which you insert instrument plug-ins (seeFig. 1). Once a plug-in is in the rack, it becomes available tosequencer tracks as a MIDI destination and an audio source, meaningthat MIDI tracks can send their data to the instrument, and theinstrument's output can be directed to an audio channel.

Other hosts (Emagic Logic and MOTU Digital Performer, for example)require you to add the plug-in as an insert in an audio track, or moreprecisely, as an insert in the mixer channel strip for that track. InLogic, MIDI and automation data reside on the audio track, and theaudio output of the instrument is managed by the track's channel strip.In Digital Performer, a separate MIDI track is used to route MIDI andautomation to the instrument, and the instrument's audio output appearsat the channel strip for the audio track.

FIG. 2: The outputs of PropellerheadReWire slave devices appear as inputs to the ReWire master device. InCubase, activated inputs (green LEDs) appear as mixer channels(left).

ReWire, though not really a plug-in format, gives you another way touse software instruments with a host application. In that context, thehost becomes the ReWire master (which is always launched first), andthe standalone software instrument becomes the ReWire slave. Outputsfrom the software instrument appear as audio inputs to the host, andwhen supported, MIDI can be transferred in both directions (see Fig.2).

LATENCY

Minimizing the latency of a software instrument (which determinesits responsiveness to input from an external MIDI controller) is oftena complex process. The greatest influence on latency is the audiobuffer size. That setting determines how much audio is stored by theaudio-interface driver before the audio is sent to the output. Largebuffer sizes reduce the processor load; small buffer sizes reduce thelatency. How to set the buffer sizes depends on your audio interfaceand the quality of its software drivers.

The computer's built-in audio drivers for all but the fastest laptopsystems (and for many desktop systems, as well) seldom produceacceptable results. You should therefore plan to use a separate audiointerface. Your MIDI interface and drivers may also affect latency,especially when intermediary software such as OMS or FreeMIDI is neededfor routing MIDI from the host to the plug-in. That's the case with MASand RTAS plug-ins as well as when linking standalone softwareinstruments to a host.

AUTOMATION

Automation is an important consideration when working with softwareinstrument plug-ins. It lets you save and reproduce various parameterchanges (such as volume and pan) that occur during playback and mixing.For software instruments, automation capability may also include any orall of the instrument's front-panel controls. If and how each of thecontrols is implemented depends on both the host and the plug-in.

Automation comes in two forms: real-time automation, which typicallyinvolves some form of MIDI control, and after-the-fact automation,which is usually accomplished by graphically editing previouslyrecorded MIDI automation (or by entering new automation data).

MIDI control allows sliders, knobs, and buttons on hardware MIDIdevices (such as control surfaces and keyboards with assignablecontrols) to change a software instrument's settings. All hosts passstandard MIDI control data such as Mod Wheel, Pitch Bend, and sustainpedal to software instruments; but not all hosts pass along all theother MIDI controllers.

That might be because the host may use some MIDI controllers forother purposes — MIDI volume and pan for control of the mixerchannel strip, for example. Another reason is that the host may reserveblocks of controllers for other plug-in slots on the same channel— for instance, to control other effects plug-ins.

Even if all MIDI data is passed to the software instrument, thesoftware instrument may not provide access to all of its controls. Thehost manual's automation section will generally tell you which MIDIdata is passed to software instrument plug-ins, and the softwareinstrument's manual will usually have a table of MIDI controllerassignments. Many software instruments have a MIDI-learn function forfreely assigning any MIDI controller to any software instrumentparameter, and some instruments even sense the type of MIDI controllerbeing used — endless rotaries or 14-bit controllers, forexample.

If you have an appropriate MIDI controller and can set up MIDIcontrol of a software instrument, you can program and edit at leastsome settings using MIDI. Beyond that, automation requires that you beable to record those changes. That amounts to recording incoming MIDIdata, and it's done in exactly the same way as when you record MIDInotes to be played by the software instrument.

The situation becomes more complex, however, when you must modifyexisting automation. Unlike punch-in replacement for notes, in whichall notes between the punch points are replaced, with automation thehost has to sense which control data to replace. Some hosts offersophisticated options for doing that; others expect you to manuallyedit out the automation you don't want. Some hosts don't provide forthat at all and delete all existing automation when a new recording isinitiated.

Another way to record automation is by changing the softwareinstrument's onscreen controls. The software instrument determines whatdata is sent to the host; some send everything, others send nothing.The host determines how and where the data is recorded, but all hostsprovide for that in some way. As with MIDI, replacing existingautomation is handled in various ways.

The third method for entering and editing automation data ismanually, using one of the host's MIDI editors. Often there is agraphic editor that displays the automation data as points connected bylines. You can typically add points, move them around, and sometimeseven change the curve of the lines connecting them.

One thing to note about the point-and-line format is that it cangenerate a huge amount of MIDI data. The lines represent smoothtransitions between the points, and entering a few points can result ina lot of automatically generated MIDI messages to create thetransition. Multiply that by the number of controls being automated,and you can quickly clog the MIDI pipeline.

FIG. 3: Most software instrument hostslet you view and edit automation in several ways. Logic is typical inproviding a list of MIDI messsages (top left), a graph (top right), anda bar chart with several editing tols(bottom).

Other editor formats that can be useful in editing automationinclude a time-stamped list in which individual points can be editednumerically and a bar-chart display that shows individual events andallows you to change their contour without adding data (see Fig.3). Editors that are combined with a MIDI transformation processor(as in most sequencers) can be very useful when editing automation. Forexample, they could let you thin, quantize, scale, and offsetautomation data without having to deal with individual events.

RENDERING

Unless you plan to restrict your use of software instruments to liveperformance, you'll want to record each instrument's output, and you'llmost likely want to do that within the same computer. That process,called rendering, is available in most software-instrumentplug-in hosts and is often built in to some instruments.

The rendering process can be handled in a number of ways. Some hostsmake you record all notes and automation before rendering to audio,whereas others let you render on the fly. Most hosts feature offlinerendering, which produces an audio file from one or more tracks of yoursong much more quickly than it takes to play it. Rendering savesprocessor power because playing back an audio file demandssignificantly less of your processor than playing a softwareinstrument.

Logic has introduced a new twist on the rendering front calledfreezing that renders an audio or software instrument track to atemporary audio file, then deactivates the original track and all itseffects. Freezing tracks that you're not actively working on enormouslyreduces processor load, greatly stretching the track count of a laptopstudio. Undoubtedly by the time you read this article, other hosts willbe offering this feature, but if yours does not, you can accomplish thesame thing by rendering then putting the rendered audio file on a newtrack and deactivating the software instrument (without deleting itsMIDI data).

For standalone software instruments, the situation is slightlydifferent. You either need to use an intermediary (such as ReWire) topipe the software instrument's audio into your audio recordingsoftware, or you must use the software instrument's built-in recordingfeatures if it has them. The latter method is less convenient andrequires sample-accurate MIDI synchronization, but it's often the onlychoice. And for recording on the fly, it might be preferable.

Although I've left the details for you to sort out for yourparticular software, you should now have a pretty good overview of whatis possible with software instruments, how to get the most out of them,and what problems you might encounter. The number and variety ofsoftware instruments is enormous, and many high-quality products arefree while others are very inexpensive. They may not yet replace allthe hardware instruments in your studio, but they can certainly add toyour collection, and for working on the road, they areindispensable.

Len Sasso can be contacted through his Web site at www.swiftkick.com.