The use of multiple computers has become common in studios today, because the power required for multiple tasks such as multitrack recording, signal processing, and working with virtual instruments (VIs) can quickly exhaust the resources of a single computer. People also use multiple computers to run applications that have been written for a single platform. A typical system might consist of a Mac running an audio sequencer such as MOTU's Digital Performer (DP) and a PC dedicated to virtual-instrument applications such as Tascam's GigaStudio or Steinberg's V-Stack. The PCs in such setups function just like hardware sound modules, and so each computer usually requires a separate hardware MIDI interface and dedicated MIDI cables. You can avoid that duplication of accessories, however, by transmitting MIDI data over a Local Area Network, or LAN.