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# Sound overview

Important

Most DOS sound cards require correct I/O base address, IRQ, and DMA settings to function. When a game’s setup utility asks for these values, they must match the DOSBox Staging configuration. See Hardware resource settings for a quick reference of the defaults and troubleshooting tips.

## Audio support in DOS games

Audio support in DOS games is a complex topic that is both fascinating and bewildering at the same time. Many competing audio solutions from different manufacturers were available on the market throughout most of the DOS-era, especially from 1987 onwards. Most of these audio devices were totally incompatible with each other and often had vastly different capabilities, necessitating game developers to add direct support for every popular device at the time their game was released. Moreover, as many of these devices were initially rather expensive, their adoption was slow and gradual. Beside supporting top of the range audio devices, developers had to add several fallback options to cater for the least common denominator cards out there, so people could get at least some sort of sound out of their games.

Although in the early days there were no standardisation efforts when it came to game audio, de facto standards did emerge over time, so the situation is not as bad as it looks at first glance. While the number of distinct audio devices DOSBox can emulate is nearing 20, many of them are niche options, and the practical gamer only needs to be familiar with the 4-5 most common ones.

But before that, we need to gain some understanding on how audio in DOS games generally works.

## Synthesised sound

Initially, music and sound effects in computer games were not stored as digitised waveforms of audio recordings (as are WAV, FLAC and MP3 files, for instance). The biggest reason for this were the memory and storage limitations of these early computers. An IBM PC with 640 kilobytes of on-board memory could store only a little more than a minute’s worth of 8-bit 10kHz digitised audio — and that would leave no space for the operating system and the program itself! Most home users could not afford a hard drive throughout the 1980s, and even when they started to become common in the early 90s, games were still coming on multiple floppy disks that could typically only hold 720kB or 1.44MB worth of data.

Yet we know that many of these games had quite elaborate, sometimes hour-long soundtracks! So how did they do it?

The solution was to store music as a series of notes instead of digitised audio. These notes would be played back by a synthesiser chip in hardware, and the chip could be programmed to assign different sounding instruments to certain notes. In essence, before the advent of the CD-ROM that could hold 650MB to 700MB of data (a vast amount for the time), or even stereo audio tracks at 16-bit 44.1kHz, all games were using hardware synthesisers for music playback.

The most well-known of these was the AdLib Music Synthesizer Card, or just AdLib in short, which was almost universally supported by all games from about 1990 onwards. Before that, the Tandy 3 Voice was the only step-up from the built-in PC speaker, but only the PCjr or Tandy versions of some games. Of course, these simple synthesisers could only approximate the sound of realistic instruments, and the result always unmistakably sounded like early electronic music.

Roland MT-32 and General MIDI music of later DOS era games followed the same basic principle, but utilising much more expensive external sound modules instead. These were the top-of-the-line sound devices of the day, capable of convincingly emulating the sound of real instruments, and producing CD-quality soundtracks in the right hands. The communication between the computer and these external modules was also standardised.

## Digital sound

Some audio cards had ADPCM decompression capabilities implemented in hardware that could cut down storage requirements to a tenth, but support was not universal across sound cards, and developers had to go with the least common denominator format, which was uncompressed audio.

## Selecting the best audio option

It is a bit less confusing to look at the best audio options separately for the three major DOS gaming eras. Naturally, these are only general guidelines and there are always exceptions, but most people would agree with this order of preference (most desirable options come first). The Getting Started guide demonstrates configuring various sound devices for a specific game.

Early DOS era (1982–1987)

- Tandy 3 Voice
- PC speaker

Late 80s / early 90s era (1987–1992)

- Roland MT-32
- Sound Blaster
- AdLib Music Synthesizer Card
- Tandy 3 Voice
- Game Blaster / Creative Music System (CMS)
- IBM Music Feature Card
- Innovation SSI-2001
- Covox / Disney Sound Source
- IBM PS/1 Audio Card
- PC speaker

Mid-90s / late DOS era (1992–1997)

- General MIDI
- Roland MT-32
- Gravis UltraSound
- Sound Blaster 16
- Sound Blaster Pro / Sound Blaster Pro 2.0
- Sound Blaster
- AdLib Gold 1000
- CD-DA
- Covox / Disney Sound Source