This has of course some disadvantages. To hear a MIDI file you need to have some information how to play the used instruments. Back in the old days the OPL2 sound chip which was present on the SoundBlaster cards was used to play the midi instruments. Most people find the sound capabilites of the OPL series rather limited and midi files were no big deal back then.4.15
Things changed when so called wavetable cards became popular. Those card have sample data stored onboard in a ROM plus a hardware mixer capable of mixing several midi channels. The MPU-401 interface from Roland is the de facto standard for accessing those cards, but this feature is not supported by OPENCP yet.4.16 A disadvantage is that those wavetable cards only have a very limited memory for sample data typically 4MB. If you imagine 127 instruments and 64 drums fitting into just 4MB you can guess what sound quality these cards have. Modern cards have normally much more onboard ROM/RAM, but in our opinion even 32MB are far too less for a good sound quality.
OPENCP goes a different way. Instead of using the onboard ROM samples, the samples needed for a specific .mid file are loaded on demand from the harddisk into main memory and then processed by either the hardware mixer (if you have such a card and the samples fit into its memory) or by the software mixers. This has the advantage that you can easily change a single instrument, if you don't like the default sound.
The instruments are stored in so called GUS-patches, a file format introduced by Gravis with their UltraSound cards. At first you have to get a complete patch set. If you own a GUS classic or GUS max you will probably have those files already on your harddisk. If not go to our homepage and download the default patch set. All instruments are stored in files ending with .pat. OPENCP needs a description of these files too in a file named ultrasnd.ini which you have to provide aswell. A sample ultrasnd.ini is listed in appendix B.
The following text will assume that you have download the gus patches from out homepage and want to install them in the default place.4.17
CD \OPENCP
ultradir=c:\opencp\patches