When I was asked to write this article, part of the brief was too see how the Panther variant of Mac OS X should be optimized for music – but such is the nature of Panther that very little optimization is actually necessary. Once you've installed a suitable audio interface that has a Core Audio driver, you're pretty much set to go – though with any processor-intensive audio application, it's as well to set the processor speed to maximum and to set energy saving settings so that the computer is unlikely to fall asleep during a vital audio operation. Assigning memory and switching virtual memory off are things of the past: OS X looks after all this for you, so most of the settings are to do with the audio interface driver rather than OS X itself.

One of the biggest mysteries to anyone new to computer audio is latency – in the case of a software instrument, this manifests itself as a delay between you pressing a key and the sound being heard. All audio software suffers from some degree of latency due to the buffering system used to create an uninterrupted audio data flow. As a rule, you can adjust the audio buffer size in the control panel for your audio interface. The smaller the buffer size, the less latency you get, which is good – but at the same time it increases the risk of audio glitching when working with multiple tracks of audio or complex software instruments. The good news is that if you're using a G4- or G5-based machine, you can probably set the buffer size as low as 128 samples without compromising system performance. In some cases, you might even be able to work at 64. At 44.1kHz sample rates, the delays produced by such buffer sizes are negligible and most users don't even notice when the buffer size is 256.

However, turn it up to 512 and you'll almost certainly notice that your software instruments seem to respond sluggishly – and when recording vocals or instruments, when you hear yourself coming back over the headphones or monitors there will be a short delay which may affect the timing of your performance. If you like experimenting, try reducing the buffer size while playing back multiple tracks of audio or software instruments. If you reach a point where glitching and clicking are evident, simply turn it back up to the next larger size.

In the old days of Mac OS 9, VST plug-ins used to be stored in a folder associated with the application that was using them. In OS X, plug-ins live in the library>Audio>Plug-ins folder, which is again subdivided according to the types of plug-ins being used. VST plug-ins have their own VST folder while Audio Units tend to live in the plug-in Components folder.

This is a better arrangement than before as every application has access to these plug-ins, though a slight complication occurs if an installer decides to place something into your personal home folder's library rather than the main library. To keep things simple, I have moved all my plug-ins to the main library where any user can access them.

If you’re moving up from OS 9, there are certain things to be aware of if songs you created under OS 9 include plug-in effects and instruments. I was in just this situation when moving up from Logic on OS 9 to OS X – and of course the first thing you have to do is get OS X upgrades for all your plug-ins. In the case of Logic, these either have to be Audio Units or OS X VST used via a 'wrapper' program, such as the one sold by FXpansion.

I've tested this with a few of the plug-ins that have yet to make the Audio Units transition, and so far it seems fine, though some software instruments seem to have trouble finding their presets under OS X whether wrapped or not. Note that there’s no wrapper that will allow an OS 9 plug-in to run under OS X. There is, however, a more fundamental irritation that I touched upon in my last piece – but it's so important that it's worth reiterating.

When you come to open old songs in OS X, switching from ASIO to Core Audio isn’t a problem – indeed, your application may offer to do it for you – but when you open the song, some or all of the old plug-ins may show up as missing, even though you know you have installed and authorized the OS X updates. The reason for this is that OS X seems to view the updated plug-ins as being completely new. So if, for example, you used a Native Instruments FM7 VST plug-in for the original song, it may open under OS X saying this isn't available, even though the OS X version is installed. When looking in the plug-in list, sure enough there's an FM7 that can be selected and loaded up in the usual way, but – and here's the catch – the host application thinks it's a completely new plug-in so it opens with a default sound, not the one you saved into your OS 9 song. I've even had this happen when running an updater for an OS X Audio Units plug-ins, so my advice is to document everything, either within the song itself or on old-fashioned paper. That way you can at least call up the correct patches manually. It's tedious, it isn’t not fun, and it's time consuming – but at least it's doable.

Software instruments
I'd like to finish by looking at the concept of software instruments, because not everyone gets the idea. Indeed, a friend from within the music industry commented to me only the other day that you couldn't seriously compare a piece of software with a dedicated hardware synthesizer that costs hundreds of pounds. I said that I agreed, but not for the reasons he imagined. A hardware synth comes with a few hundred megabytes of sound ROM at best, most are programmed via inadequately small screens, and far too many of them have badly designed audio electronics resulting in higher levels of hiss and hum than I consider acceptable.

By contrast, a software instrument sounds as good as the converters in your audio interface, it may come with several gigabytes of sample data and the user interface can occupy a full computer screen if it needs to – you are no longer limited to a 16 character, two-line LCD window. Additionally, any changes you make to the presets are remembered in the song when it’s saved; you have virtually unlimited memory for storing your own sounds; and rather than deteriorate with age, the instrument is actually likely to improve as upgrades become available.

True, a sophisticated software instrument can take a lot of processor power, but a fast G5 costs no more than some high-end keyboard synths – yet it can host an entire studio providing you with a multitrack recorder, MIDI sequencer, automated mixer and more effects and instruments than you'd ever be able to afford (or find room for) in the hardware domain). I rest my case!

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