Ever get the urge to play one of your synth plug-ins without having to go through the rigmarole of booting up your full DAW? Chainer (Win, $60.00), Rax (Mac, $29.95), and SynthTest (Mac, free) are each designed for just that. Chainer is a Windows application that hosts VST instrument and effects plug-ins. Rax and SynthTest host Audio Units (AU) instrument and effects plug-ins in Mac OS X; you can use VST plug-ins with them, too, if you use a wrapper such as FXpansion's VST-AU Adapter (www.fxpansion.com).
Manyetas SynthTest 1.2.1 (www.manyetas.com/creed/synthtest.html) is the simplest of the three to use. It allows you to run one AU instrument and one AU effect. Just open SynthTest, load your plug-ins, select a MIDI source, and off you go. You can load and save presets directly from SynthTest's control panel, which offers no other controls such as volume or pan. However, you can usually open the plug-in's control panel for those functions as well as preset editing. SynthTest is open source and is intended primarily as a developers' tool, but it's an excellent AU host in its own right.
Granted Software's Rax 1.0 (www.grantedsw.com/rax) presents you with a 16-channel rack into which you can install AU instruments, insert effects, and send effects. Menus for MIDI input and audio output let you select among all installed devices. MIDI can be sent to instruments and effects (for MIDI automation), and each item in the rack can receive on any or all MIDI channels. The rack contains a built-in 16-channel mixer; when an instrument is installed, it is automatically wired to the next free mixer channel. Each channel has eight send buses, and multiple effects can be inserted in each bus. Insert and master effects buses are also available. Depending on your audio interface's capabilities, you can even plug multiple channels of live audio into the rack. You can download a free version of Rax that will host a single AU instrument and one mono or stereo audio input. Registration enables full multi-instrument capability.
Xlutop Chainer 1.03 (www.xlutop.com/html/chainer.html) is similar to Rax in that it allows you to play several VST instruments at the same time and lets you follow them with multiple VST effects plug-ins. It enables you to create complex signal paths, and you can use it to process ASIO audio input. Chainer runs as a standalone application, and VST plug-in versions for instruments and effects are provided as well. Using Chainer, you can create complex effects chains within other VST host applications. Download one of these handy utilities, and when that postmidnight urge to play one of your synths strikes, you will be prepared.