Connect your keytar to the computer using the USB or USB-to-MIDI cable. The cable you will use depends upon the model of keytar that you have. Many newer digital instruments now include USB outputs. MIDI information is quickly sent over USB cables and it is now a more commonly used format. Older keytar models will use the standard MIDI Ins and Outs, and a converter cable will be required for connecting to a Mac or PC.
Choose and install your synthesizer program. Propellerhead Reason 5, FL Studio and Garageband (see the Resources section) are three digital music programs (Garageband being a live audio program with MIDI capabilities). Many others are available that use generic MIDI drivers to detect and work with digital instruments, including the keytar.
Download and try out demo versions of the software before purchasing a full version. All synthesizer programs may be used for the same thing, which is to perform and compose digital music. However, they use different methods of doing so. Make sure that whichever program you decide to buy is one that you are comfortable using.
Assign your keytar as the input device used to control your synthesizer program. Open the "Preferences" menu in "Propellerhead Reason" to access the list of MIDI instruments that can be used with it. Select "Keyboards and Control Surfaces" under the "Pages" tab and choose the keytar to control your synthesizers. If it is not listed by name choose the "Generic MIDI Device."
Use the keytar with FL Studio by going to the "MIDI Settings" menu in the "Options" tab. Again your keytar should be listed either by name or as a generic MIDI controller in the input list. Click the "Enable" button beneath the list to choose the keytar as one of the instruments that you would like to control FL Studio with.
Create a new track called "GarageBand" in the "Track" window and choose "Software Audio Track" to use your keytar. GarageBand will auto-detect the instrument. All you have to do from here is choose a sound effect.