OMS Associates Information with Device Names An important aspect of OMS is that it associates all MIDI information pertaining to a specific device—such as port and channel assignment—with each device’s name. You simply choose the name of the device you want to record or playback; whereas, without OMS, you’d have to choose the port and the channel, which entails having to remember the device hooked to that port and the channels it’s transmitting on. When you choose an OMS device name in a Metro pop-up menu or dialog box, Metro automatically knows the necessary information about that device and can send and receive data without your having to remember what port that device is hooked to, the channels it’s transmitting/receiving on, whether it sends or receives sync, and so on. For example, you can choose your Thru Output by name only; Metro immediately knows where to play it.