DOSBox sound emulation
Discover sound and audio hardware and why it is probably one of the more complex and irritating elements of DOS gaming in the early 1990s.
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Sound and audio hardware was probably one of the more complex and irritating elements of DOS gaming in the early 1990s. So many choices, incompatibilities, and even different advantages for sound effects, speech, or music. So what do you choose today when an emulator like DOSBox gives you so many audio choices?
This entry will describe the significant sound cards that impacted the DOS era of PC gaming, a brief history and their compatibility with DOSBox. I will also create a chart that will list, in my opinion, the best music and sound effect emulation options for your gaming titles.
PCM – Pulse Code Modulation is a digital representation of an analogue sample, also used by audio CDs and occasionally on DVDs.
DAC – Digital to Analogue Converter used for playing back digital sound and music through standard speakers and headphones.
ADC – Analogue to Digital Converter used for recording samples from a standard microphone and storing it in a digital format on the computer.
DSP – Digital Signal Processing or Processor. It is essentially DAC and ADC combined, which allows for both digital-to-analog playback and analog-to-digital recording.
Channel – A single music instrument or sound sample.
FM synthesis – Frequency Modulation synthesis generates and distorts an audio tone to fake an instrument, often used on synthesises from the 1980s or earlier, and has a very electronic, artificial sound.
LA synthesis – Linear Arithmetic synthesis uses filters to manipulate pre-recorded digital sample sounds.
Wave-table synthesis – In PC audio, it refers to pre-recorded sounds and samples or instruments that are manipulated for tone and pitch.
Introduced as the only form of audio output on the original IBM PC in August 1981. The PC speaker could only play one waveform tone simultaneously, making it useless for music and gaming. The notoriety of the speaker’s quality would later earn it the titles PC squeaker and the PC beeper.
Given what was available on other, cheaper computers at the time, one can only assume this offering by IBM was a form of cost-cutting. However, the PC’s target market was business applications, so it is understandable why IBM initially chose to ignore audio in its original PC specification.
Unfortunately, this limited audio ability would later haunt PC gaming, and it would take over a decade for improved audio replacements to become standard.
Developers did find hacks around the limitations of the PC speaker, with various games of the era managing to reproduce multiple-toned music, digital sound-fx, and even speech. At best, these hacks produced a 6-bit, single PCM, DAC-like channel. Unfortunately, various implementations suffered from problems that limited their usage.
These hacks were often CPU speed-sensitive, whereby a processor could be too fast or slow and would distort or warp the audio output. There were no volume adjustments, only an on-off switch in the computer’s BIOS. The output volume was often too quiet, making the audio hard to hear as the PC’s speaker was placed deep inside the steel casing of the desktop.
A bargain basement Commodore VIC-20 from the same era came with a retail price of US$299.95. In comparison, the IBM PC started with a retail price of $1,565 for a base model. Yet the VIC-20 has significantly better audio capabilities than the IBM.
DOSBox emulates all functionality of the PC speaker, including the PCM-like DAC hacks, though usually, you will need to manually adjust the DOSBox speed (cycles) settings to get it working correctly. Dunzhin: Warrior of Ras Volume I by Computer Applications Unlimited from 1982 is an early example of DAC playback through the PC speaker.
Tandy 1000 / Tandy DAC
The original Tandy 1000 series of computers that first came out in 1984 upgraded the internal PC speaker to three channels plus white noise. Later models also allowed for external volume control and support for headphones. The Tandy 1000 audio improves the default PC speaker when implemented in software.
In 1989 Tandy released the 1000 SL series of computers that updated their 3-channel audio chip to incorporate an onboard 8-bit, mono DAC/ADC for digital sampling and playback. Several games, including a few Sierra titles such as Space Quest III, support this improvement. They experimented with it for a brief period before the Creative Sound Blaster went retail and drew Sierra’s attention elsewhere.
DOSBox emulates both Tandy audio (3 channels) and Tandy DAC.
I recommend setting the DOSBox.conf to use
tandy=true rather than
tandy=auto to force older games to auto-detect the Tandy 3-channel audio. You might also have to set the DOSBox
For Tandy DAC, DOSBox also requires that
sbtype= is set to any allowed value other than
SimCity sound effects compared, PC vs Tandy
Covox Speech Thing / Disney Sound Source
The Covox Speech Thing was a simple 8-bit DAC/ADC adapter plugged into a PC’s parallel printer port. Initially released in 1986, it was later revised and marketed under various companies and brands. Including Disney, who in the early 1990’s sold the Covox for use with their educational software.
Note that a few games out there support similar devices called the Covox Voice Master and the Covox Sound Master. These are internal sound cards rather than printer port adaptors with no emulation. DOSBox mimics the Covox printer devices, including The Disney Sound Source, which offers better audio quality.
AdLib / OPL2 / YM3812
Introduced in 1987, the AdLib Music Synthesizer Card was the first add-on music card to gain widespread support within the PC industry. While it wasn’t the first, nor the most popular, it became the de-facto standard for software developers in the early 1990s when music and sound card support first became common.
Early games often require an AdLib driver known as a DOS TSR (Terminate and Stay Resident) in order to implement support. But later, games included and loaded their internal audio drivers. The card used a Yamaha YM3812 9-channel FM synthesis chip which is also known as the OPL-2.
In 2022, MobyGames states that in 1987 there was only one game with AdLib support. By 1988 there were eight games, but by 1989, there were almost 100 and nearly 200 games in 1990!
DOSBox emulates AdLib audio. AdLib emulation is set using the
oplmode=auto setting in the DOSBox.conf file to control emulation.
oplmode=opl2emulates the original AdLib that the original Sound Blaster also uses.
oplmode=dualopl2emulates two OPL-2 chips used by the first generation of Sound Blaster Pro cards.
oplmode=opl3simulated the AdLib Gold series of cards and was also used by the Sound Blaster 16.
Roland MPU-401 Interface; MT-32 / MT-100 / CM-32L / CM-64 / LAPC-I
DOSBox supports the MPU-401 (MIDI Processing Unit) interface created in 1984 by the Japanese audio company Roland to enable customers to connect MIDI-compatible devices to their home computers. Initially, this interface support was through standalone cards, but partial support was later incorporated into many third-party sound and joystick add-on cards.
The Roland MT-32 Multi-Timbre Sound Module from 1987 was a programmable synthesiser that supported up to 32 notes played at once using a 16-bit DAC at a sample rate of 32000 HZ. This standalone device required an MPU-401 interface installed on the host machine to connect to and use on a PC.
Also from Roland this year was the MT-100 which for our purposes is the same MT-32 device in a different form factor.
Many DOS games from the period supported music playback using Roland’s famed MT-32 sound module, as the audio quality output was better than the competing but cheaper AdLib sound card. Unfortunately, the expensive combination of the MT-32 sound module and the required MPU-401 compatible interface card meant support wasn’t as widespread.
The Roland LAPC-I (Linear Arithmetic Personal Computer IBM) from 1989 was a PC card that joined the MPU-401 interface card with a near-compatible MT32 sound module and incorporated both their functionalities into a single, easier to set-up device.
Also, in 1989 Roland released the first of a series of CM (Computer Module) sound modules. Some of which improved but were also mostly compatible with the MT32 module. Models included the CM-32L, an improved MT-32 with 33 added sound-effect samples. And the CM-64 was a more expensive model of the CM32L with extra functionality geared toward computer musicians.
To complicate things, MPU-401 has two modes, ‘intelligent’ and ‘UART,’ otherwise called dumb mode. Many ‘MPU-401 compatible’ cards and devices only support UART mode. In UART mode, the attached MPU-401 component acts as a dumb playback device.
While the intelligent mode, the attached device handles part of the audio processing. This more complex mode allows computers with the slowest generation of Intel PC CPUs (such as the 8086 and 8088) to handle MIDI playback. But intelligent mode had become redundant when support for these CPUs was abandoned in favour of faster chips that could handle the audio processing.
Many legacy DOS games of the late 1980s expect the intelligent mode for MT-32 audio playback. To get around this, many of these games have post-release software hacks known as patches that enable them to use an MT-32 sound module attached to a computer with a UART-only MPU-401 connection.
Fortunately, DOSBox can emulate both MPU-401 modes using the
mpu401=uart settings. So you can attach an MT-32 or compatible sound module to your computer to receive accurate music playback but avoid patching the games.
Creative Music System / Game Blaster
Creative Music System, released in 1987, was the first add-on sound card by the Singaporean-based company that would later become Creative Labs. The card used two Philips SAA 1099 chips that each supported six channels of waveforms in stereo. Price at a similar level to the AdLib, the CMS audio was of poorer quality, so it never gained broad industry support.
MobyGames game support: in 1987, there was one game with CMS support, 4 in 1988, and under 20 in 1989. By 1990 there were over 40 games, but this dropped to under 20 titles in 1991 after Creative’s own Sound Blaster card supplanted it.
DOSBox emulates CMS sound, but it needs to be enabled by modifying the
oplmode=cms in the DOSBox.conf file. This change disables AdLib audio.
Sound Blaster 1 / 2
Sound Blaster 1.0 first appeared in 1989 and was the successor to the not-so-popular Creative Music System, later known as the Game Blaster. The Sound Blaster 1.0 was a kind of hybrid card in that it offered backward support for its earlier Game Blaster series. It also had the Yamaha YM3813 chip in the more popular AdLib card.
In addition, Creative also included a digital signal processor allowing the playback of sampled sound at 23kHz and recording at 12kHz. It is priced in retail at the same level as the AdLib and added value add-ons such as a built-in game port. The Sound Blaster out-valued and out-featured its rival, eventually forcing the AdLib company to file for bankruptcy.
MobyGames game support: 1 in 1988, under 20 in 1989, over 60 in 1990 and well over 150 in 1991.
As a cost-cutting measure, the Sound Blaster 1.5, released in 1990, did not include the chips that enabled legacy Game Blaster support. But these chips could be purchased separately from Creative and attached to the device by the user.
The Sound Blaster 2.0 was released in 1991 and offered improvements to the digital signal processor chip. It upgraded the playback to 44kHz in 8-bits and allowed for auto-DMA, removing an unwanted clicking sound audible in earlier cards.
Sound Blaster Pro
Sound Blaster Pro was the successor to the Sound Blaster series of cards, introducing stereo-like playback. Like the earlier CMS line of cards, it used two YM3812 chips to emulate stereo. But games had to be programmed to use this feature; otherwise, they would play back in mono off a single chip. The updated Pro DSP chip allows for 44kHz, 8-bit samples in mono, or 22kHz samples in stereo.
Sound Blaster Pro 2.0 removed the twin YM3812 chips and replaced them with a single Yamaha YMF262 chip, otherwise known as the OPL-3. It allowed for 20 FM synthesis channels played back in stereo.
DOSBox emulates the Sound Blaster 1, 2, and Pro.
sbtype= allows you to force Sound Blaster emulation manually.
sbtype=sb1emulates the original mono Sound Blaster.
sbtype=sb2emulates revision 2 of the same card.
sbtype=sbpro1emulates Sound Blaster Pro.
sbtype=sbpro2emulates revision 2 of the card.
sbtype=sb16emulates the Sound Blaster 16.
Pro AudioSpectrum (PAS)
Created by the Californian-based Media Vision. The first Pro AudioSpectrum released in 1991 was an 8-bit stereo card that used two YM3812 chips for FM music and had its custom DSP chip. I am pretty sure the DSP chip was stereo, but a lack of Sound Blaster compatibly limited its appeal.
It did, however, include a SCSI CD-ROM interface allowing the connection of a new to-the-market CD-ROM drive. At this time, there were significant savings for buyers who purchased a Pro AudioSpectrum for use with a CD-ROM drive instead of a SoundBlaster Pro with a separate SCSI card.
There is no AudioSpectum emulation in DOSBox.
Sound Blaster 16
Released in the middle of 1992, the 16 series was the next major upgrade to the Sound Blaster range of cards. It finally saw Creative catch up to its competitors by offering 16-bit, 44kHz playback, while music playback improved with the standard Yamaha OPL-3 chip. The card came with the usual Creative price markup at retail, but it offered official backward compatibility with the earlier Sound Blaster series.
DOSBox emulates SoundBlaster 16 audio.
Gravis Ultra Sound
In 1992 Advanced Gravis, a well-known Canadian joystick company released the physically large, bright red Gravis Ultra Sound add-on card. Priced slightly higher than the Sound Blaster Pro, the Ultra Sound gave owners a significant bang for their buck. Unfortunately, this added value was at the expense of Sound Blaster compatibility, which left most new owners with a collection of games with limited or no audio support.
The card itself was a wave-table sound card with 256KB of RAM built-in. Unlike its competitor, the Sound Blaster AWE-32, the Gravis did not come with pre-saved samples; everything had to be loaded through software drivers or by the game itself. As the card did not offer hardware emulation for the Sound Blaster DSP chip or ancient AdLib OPL-2 music chip, all legacy audio had to be emulated using uploaded samples. This process required extra computer memory and CPU resources and often utilized hacks to partially get many unsupported games to work. As such, some owners of the Gravis would additionally install a cheap Sound Blaster clone on their PC for better gaming compatibility.
On the plus side, when games did offer support for the Gravis, it provided a far greater audio capability than anything else on the home consumer market. It allowed for 14 channels at 44kHz playback or 32 channels at 19.2kHz.
Several games require the use of Gravis drivers, and as copyrighted software from a commercial company, these drivers are not included with the open-sourced DOSBox installation. You need to install the drivers within DOSBox session to a subdirectory and afterwards change
ultradir= to point to this directory path in Windows, macOS or Linux.
- Gravis UltraSound Drivers disks on WinWorld
- VOGONS Gravis UltraSound tool collection part 1 and part 2
- Gravis UltraSound installer CD
Sound Blaster AWE32
In early 1994 Creative released the Sound Blaster AWE32. It acted as a Sound Blaster 16 with a built in synthesizer board and effects chip. These enhancements were useless unless the game directly supported them, which was a rarity. The card came with a 1MB sample ROM and 512KB of RAM for user samples. It used 30 sampled channels plus an additional two channels for the FM OPL-3 synthesizer.
It could also attempt to emulate General MIDI and MT-32 audio playback using software drivers. The drivers required for this consumed valuable conventional memory and could not work with typical 32-bit protect mode DOS programs.
A budget version of the card known as the Sound Blaster 32 was released in 1995. It removed the onboard RAM and support for bass, treble and gain adjustments.
There is no DOSBox emulation for the AWE32 series.
General MIDI – GM
It is an enhanced and standardised specification for MIDI (Musical Instrument Digital Interface). It assigns specific instruments to MIDI program messages so that any General MIDI device receiving program message 18 will always play a rock organ and program message 28 will always be a muted rock guitar.
Codified in 1991 by the MIDI Manufacturers Association and Japan MIDI Standards Committee, the GM standard was made redundant on release by Roland’s improved and compatible GS format.
One of GM’s major problems was the lack of quality requirements on the timbres used. So the instrument representation on a GM device could greatly vary in quality from manufacturer to manufacturer.
Many DOS games from the 1990s support General MIDI, but their music reproduction varies depending on the GM device used for playback. Most game musicians composed their tracks on Roland Sound Canvas products, making those devices a good bet for accurate playback.
Roland General MIDI only playback products.
- SC-7 Sound Module from 1992 was unique as it allowed a connection to the PC or Mac using a serial port.
- RAP10/AT Roland Production Audio Card from 1994 included a stereo 16bit 44.1kHz DSP.
Roland GS – Sound Canvas
Created in 1991 and pushed by Roland, the proprietary GS format is a backward compatible extension to General MIDI. GS products even reached the consumer market first and the format allowed for more varieties of instruments than GM, plus it gave Roland flexibility for future enhancements.
The Sound Canvas, with its famous SC series of cards and modules, was the branding Roland most used to push consumers to the GS format. Confusingly, there were many GS-compatible products to target various segments of the market, from home consumers to professional musicians. So the few DOS games that support playback on GS devices generally list Sound Canvas support and not the specific models.
Select Roland Sound Canvas MIDI Sound Generator GS modules.
- SC-55 from 1991.
- SC-155 from 1992.
- SC-55 Mark II from 1993.
- SC-50 from 1993.
- SC-88 from 1994.
Select Roland computer modules.
- CM-300 from 1991 was GS compatible.
- CM-500 from 1991 was GS and LAPC-I compatible.
Select Roland GS Sound Canvas PC Cards.
- SCC-1 from 1991.
- SCP-55 from 1995.
First released to the public in 1994, the XG format is another proprietary extension to the General MIDI standard. While it offered a greater variety of instruments than either GM or GS, it was never directly supported by DOS games. However the product’s General MIDI playback performance was different enough for the format to earn its gamer fan base.
General MIDI Emulation
Operating systems of the late 1990s and 2000s included MIDI drivers and software playback in the core system. Windows once had Microsoft GS Wavetable SW Synth based on a product from Roland. In comparison, OSX used QuickTime Music Synthesizer. As of 2022, neither Microsoft nor Apple licenses nor includes MIDI support.
Windows Media Player in Windows 11 still is happy to play MIDI tracks. And Windows users can also use the free OmniMIDI freeware driver for professional use.
DOSBox Supported Devices … which are the best to use?
These charts are a matter of personal opinion. They are based on running DOSBox v0.74 under a legacy Windows host system with a Sound Blaster Audigy 2 and a pair of amplified stereo speakers. Of course, the audio quality will also depend on the software or game operating under DOSBox.
|1||Roland Sound Canvas (physical device)|
|2||Gravis UltraSound (with correct ROMs)|
|3||General MIDI (software emulation)|
|5||Roland MT-32 (physical device)|
|6||Sound Blaster 16 / Sound Blaster Pro 2 / OPL-3|
|7||Roland MT-32 (when mapped to a GM driver)|
|8||Sound Blaster Pro|
|9||Sound Blaster / AdLib / OPL-2|
|10||Creative Sound Master / Game Blaster|
|#||Sound effects and speech|
|2||Sound Blaster 16|
|3||Sound Blaster Pro|
|5||Disney Sound Source, Covox Speech Thing, Tandy DAC|
|6||Tandy 1000, Creative Sound Master, Game Blaster, PC speaker|
Written by Ben Garrett