Although it is difficult to clearly quantify distinctions between synthesizers, it is important to have some guidelines so you can create MIDI files that will play on all multimedia computers. The terms used to distinguish synthesizers for the purpose of authoring MIDI files are base-level synthesizer and extended synthesizer.
The distinctions between base-level and extended synthesizers are made solely on the number of instruments and notes the synthesizer can play, not on the quality or the cost of the synthesizer. The following table shows the minimum capabilities of base-level and extended synthesizers:
| Synthesizer | Melodic Instruments | Percussive Instruments |
| Number | Polyphony | Number | Polyphony | |
| Base-Level | 3 instruments | 6 notes | 3 instruments | 3 notes |
| Extended | 9 instruments | 16 notes | 8 instruments | 16 notes |
Polyphony is the number of notes the synthesizer can play simultaneously. The polyphony expressed above applies to each group of instruments—melodic and percussive. For example, a base-level synthesizer is capable of playing six notes distributed among three melodic instruments and three notes distributed among three percussive instruments. The melodic instruments are each on different MIDI channels, and the percussive instruments are key-based—all on a single MIDI channel.
All multimedia computers provide at least a base-level synthesizer. Users can enhance their computer by adding internal or external synthesizers, which can be either base-level or extended synthesizers. When a user adds a synthesizer, the user must configure the MIDI Mapper to use the new device, or the instrument sounds will not be correct when playing MIDI files. The MIDI Control Panel applet allows a user to configure the MIDI Mapper as needed.