MIDI Output

MIDI Output is used in Overtone Analyzer to create sounds for the keys of the piano keyboard and for the Overtone Sliders. You may find that the sound of the piano and of other instruments is not very good. This page discusses a few possibilities for improving the sound of your instruments.

Basics of MIDI Output

MIDI stands for "Musical Instrument Digital Interface". It is an industry-standard electronic communications protocol that enables electronic musical instruments, computers and other equipment to communicate, control and synchronize with each other in real time (Wikipedia).

Contrary to other audio formats, MIDI does not transmit the actual audio signal or waveform to be played. Instead, it simply transmit a series of event messages such as "play a piano sound with the note 'C' for 1 second". If you play back the recording of a real piano performance, it will sound very similar on all players, and differences in sound will only depend on the quality of the playback system and the speakers.
If you play a MIDI file of a piano performance, the actual sound is not stored in the MIDI file, but in the piano instrument of the player. In that sense the MIDI file is more similar to the musical score of the piece than to a recorded performance. That's why a MIDI file can sound completely different on various players, as the different players may have a different idea of what a piano (or other instrument) sounds like.
Also, MIDI files don't normally contain any vocals, because the human voice cannot (yet) be synthesized properly (many synthesizers cannot even get the standard instruments to sound right).

Synthesizer Technologies

To say it once more, the sound of a mp3 or wav file is determined by the recording and is stored in the file itself. In contrast, the sound of a MIDI file is determined by the used MIDI player (or synthesizer). That's why it is so important to select a good synthesizer for MIDI playback.

There are two main kinds of generating the instrument sound during MIDI playback: Wavetable Synthesis and Physical Modelling Synthesis.

Wavetable Synthesis

This method starts with a digital recording of a real instrument such as a piano. In some cases every key of a piano is recorded at different loudnesses, so that loud and soft notes can be played accurately. With a good speaker system, a synthesizer of this kind can sound as good as a recording of the real instrument, because that is basically what it is. Many digital pianos use wavetable synthesis.

Physical Modelling Synthesis

Instead of using recordings of real instruments, this method attempts to simulate the sound of the instrument through mathematical equations. The simplest example is a sine wave generator, which sounds somewhat similar to a flute. It can be difficult to obtain convincing imitations of real instruments with this method. On the other hand it allows completely new instruments that have no physical equivalent and may also sound very interesting.

Midi Output Device

If you press F3 to open the Device Options Dialog, you can see the selected MIDI Output Device:

Device Options
Figure 1: Device Options

There you can also see a list of all the available MIDI Devices that are installed on your system.

Microsoft GS Wavetable SW Synth

If the output device is "Microsoft GS Wavetable SW Synth", your soundcard has no dedicated facilities for playing back MIDI, and all MIDI sounds are created by this software synthesizer. The sound quality of this might be usable, but is probably not very good. This has a few reasons:

  • The internal software synthesizer needs to run on a large variety of system configurations, and some may not have much processing power or memory. Therefore this synthesizer needs to have very low resource requirements and consume very little CPU time and memory. This means the sound quality of the MIDI instruments that come with this synthesizer is probably quite low to save resources. You might get better quality by using a different software synthesizer with higher quality instruments (see below).
  • If you are using the internal software synthesizer, you are probably also using a cheap standard soundcard, possibly connected to cheap computer speakers. This is a working minimal setup for playing back sounds on your computer, but it simply won't sound very good. You will probably get better sound by upgrading your sound card and your speakers.

Sound card with Hardware MIDI Support

Some sound cards, such as the Soundblaster Live! and Audigy families, have hardware support for playing back MIDI instruments. This means that the sound card can play back high quality recordings of an instrument without using much CPU time. You can also load your own instruments into the card in the form of Soundfonts.

MIDI Keyboard / Digital Piano

If you have a midi keyboard or a digital piano, you can probably connect it to your computer and select it as the MIDI Output Device in Overtone Analyzer. Instrument sounds will now be played through your keyboard or piano instead of your computer speakers, which may sound much better.

Installing your own software synthesizer

Even if you don't have a MIDI keyboard or an expensive sound card, you can improve the sound of your MIDI playback by installing your own software synthesizer. There are many free and commercial software synthesizers available on the web. Often they mainly use one of the two discussed methods of either wavetable synthesis or physical modelling synthesis, although some use both methods. We will give examples of how to install a soundfont player that can use recordings of real instruments, as well as how to install a physical modelling synthesizer that has a more electronic sound but offers very interesting instruments and effects.