Sticking with older Mac OS versions has its own hazards — it leaves users standing in the shadow of a Tower of Babel that has existed for more than a decade. Software and hardware developers have largely been on their own in making sure that sophisticated MIDI and audio peripherals work well on the Mac.
For MIDI, users formerly looked to Mark of the Unicorn (MOTU) and Opcode to supply system software components that support MIDI interfaces and integrate MIDI instrument management in Mac OS applications. The risks of having developers alone manage that crucial task became all too real when Opcode shut its doors last year, taking active support of its Open Music System (OMS) software with it.
Audio support has arguably been even more confusing. Confronted with the Mac system's Sound Manager and its latency problems, lack of multichannel compatibility, and inability to handle full-duplex recording and playback, audio companies had to develop their own software interfaces. They did pretty well, creating low-latency audio systems such as ASIO and EASI to implement multichannel audio-card support without requiring a particular brand of hardware. (In fairness, however, ASIO and EASI exist to work around the limitations of Mac and Windows.) Other companies, including Digidesign, took a walled-garden approach that consisted of proprietary integrated hardware and software products for musicians who wanted an extra measure of performance and reliability.
Plug-ins for software effects were even more befuddling. Unlike Microsoft, with its DirectX format for Windows (leaving aside its particular pros and cons), Apple offered no systemwide software plug-in format. A sometimes bewildering array of mutually incompatible plug-in formats — including Steinberg VST, MOTU Audio System (MAS), and Digidesign Real Time AudioSuite (RTAS) — appeared to fill the vacuum. In general, they worked well, but many desktop musicians wondered why Apple didn't take a more active role.