Some internal MIDI synthesizer devices cannot keep all of their patches loaded simultaneously. These devices must preload their patch data.
Windows provides the following functions to request that a synthesizer preload and cache specified patches.
| Value | Meaning |
| midiOutCachePatches | Requests that an internal MIDI synthesizer device preload and cache specified melodic patches. |
| midiOutCacheDrumPatches | Requests that an internal MIDI synthesizer device preload and cache specified key-based percussion patches. |
For information on how to determine if a particular device supports preloading patches, see Querying MIDI Output Devices.