Although it is difficult to clearly measure differences between synthesizers, you need some guidelines so you can create MIDI files to play on all Multimedia PCs. For this purpose, two types of synthesizers have been defined: Base-level synthesizer and Extended synthesizer.
All Multimedia PCs 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.
The distinctions between Base-level and Extended synthesizers depend solely on the number of instruments and notes it can play, not on its quality or cost. 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.
Melodic instruments are each on different MIDI channels; percussive instruments are key-based—all on a single MIDI channel.
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 Mapper Control Panel applet allows a user to configure the MIDI Mapper as needed.