Connect the Kurzweil K2600 keyboard to your computer using the MIDI connectors in the rear of the keyboard. Connect the USB Midi cable to the five pin connectors in the rear of the keyboard marked "MIDI in" and "MIDI out". Run the cable to your PC and connect the USB end into your PC.
Turn on the PC and wait for the operating system to boot up. Install a computer sequencer capable of interpreting MIDI input from your keyboard. No sequencer is inherently better than the others, but some use different methods for presenting and inputting musical sequences. Pick a sequencer that uses a method that you're comfortable or familiar with, such as traditional notation on a music score or as musical loops. Download a demo of different sequencers to explore the features before purchase.
Set up your sequencer to use the keyboard as an input device. This allows you to control the sounds created with the sequencer through a musical keyboard. You can still alter the instruments used in your compositions by selecting different instrument in the sequencer itself.
Compose a piece of music. Switch to the musical score screen for ease of use with the keyboard. Choose a musical key to record in and choose an instrument. Lay down your first track of music by playing what you want using the keyboard. The computer sequencer will transcribe what you play note-by-note onto the musical score. Play back the track to make sure it's what you wish, then save the file. The K2600 has full-sized, weighted, pressure-sensitive keys that give it the same feel as an actual piano. Playing the keyboard as a piano will translate note volume and note starts and stops directly into the sequencer.
Open a second track in the file, again using the musical score input selection. Choose an instrument, and play an accompanying piece to your first saved track. You can play it solo, or set the sequencer to play along, listening to the first track while you input the second. Play back the new track, either alone or in concert with the first track, to listen to the dual track musical piece.
Build up your musical piece in this way, laying additional tracks onto the first. You can alter the tracks using the sequencer tools, removing or replaying sections of the track, or altering a single note if necessary. You can import .WAV files, which are digitally recorded audio files, into the sequencer and use them as tracks as well to add vocal sequences or pre-recorded sections of music.
Save your creation in the audio file type of your choice for later playback with a compatible media player.