The USB Midisport 2x4 is a compact bus-powered, multi-port MIDI interface for USB-equipped PC and Mac computers that's perfect for laptop music-making. The unit's 2 x 4 architecture also lets you go beyond the MIDI spec's limit of 16 channels. Two separate
16-channel input ports allow your system to accept up to 32 discrete
MIDI input channels. And four individual 16-channel output ports allow
you to address up to 64 discrete MIDI output channels

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