Custom PC - UK (2020-01)

composersfromdoing

remarkablethingswithit.

Beyondsimplesystem

beeps,theeasiestmusicto

persuadea PCspeakerto

reproduceis single-tone

melodies.A seriesof

instructionsis senttothe

timerviatheCPU,usingthe

programminglanguageof

yourchoice,tellingtoit

producea seriesoftones

ataspecified frequency.

Sound effects in games

alsostartedoutassimple

beeps,butprogrammerssoon

startedgettingclever,rapidlychangingthetonesbeing

senttothespeakertoproducecomplexaudioeffects.

ApogeeGamesmasteredtheartofcreatingconvincing–

oratleastdistinctive– PCspeakereffectsintitlesincluding

CommanderKeenandHocusPocus.

Youtechnicallycan’tplaypolyphonicmusiconhardware

thatcanonlyproduceonevoiceata timebut,asit transpires,

therearewaysaroundthisproblem.Probablythemost

widelyusedapproachtothisis arpeggiation,wherea

pseudo-polyphoniceffectis achievedbyrapidlyswitching

fromonetonetoanother– anywhereupto 120 timesa

second– togivetheimpressionofchordstothelistener.

A numberofgames,includingthe 1990 PCversionof

TheBitmapBrothers’Xenon2 Megablastin1989,thePC

portofSega’sGoldenAxeinthesameyearandMagnetic

Fields’LotusIIIin1992,createtwoorthreevirtualaudio

channelsandalternatewhichofthemisdirectedtothe

timerchip,allowingbasslinestoberapidlyswitchedinto

themusic.Theresultsoftensoundharshandbusy,but

producea rathereffective

impressionofpolyphony.

A combinationofthese

techniqueswasusedtoeven

bettereffectinLucasArts’

PCspeakermusic,such

astheremarkablebeeper

renditionofthemaintheme

fromTheSecretofMonkey

Island(1990),wherethe

sophisticateduseoffast

trillsandanalternating

percussivechannelcreated

theimpressionofsteel

drumchordsbacking

themainmelody.

Othertechniquesmade

moredirectchangestothewaythePCspeaker’ssound

outputworked.WindmillGames’ 1983 bootergameDigger

anditsiconicuseofHotButter’sPopcornasitsin-game

themeis thoughttobetheearliesttitletousepulsewidth

modulation (PWM) as a

method of producing

more sophisticated

sound, with a variable

volume and harmonies.

Also used in

numerous ZX

Spectrum games, PWM

uses careful timing of

the signals sent to the

PC speaker to modulate

its usually binary

voltage levels, forcing the speaker into a range of partially

on positions to produce sine waves. This can effectively turn

thespeakerintoa 1-bitDAC(digital-to-analogueconverter).

AlsoheardintitlesincludingHardDrivin’andFantasy

WorldDizzy,thisapproachcanbeusedtoplaya pre-

generatedsoundtrack,ratherthanusingthetimerchipto

directlygeneratesquarewavetones.However,evenat1-bit,

thissoundreproductionwasoftenCPU-intensiveandthe

resultingaudio’slowqualitygratesonmanylisteners.

Later,AccessSoftware’sRealSoundtechnologyuseda

near-inaudiblecarrierwaveandfine-grainedcontrolofthePC

speaker’sdisplacementamplitudetoproduce6-bitdigitised

audio,givingussurprisinglyhigh-qualityspeechandmusicin

gamesincludingMeanStreets,WorldClassLeaderboardGolf

andLegendEntertainment’sSpellcastingseries.

By1992,evenMicrosoftwasinonthegame,releasinga

driverforWindows3.1thatallowedanyPCMWAVfiletobe

outputviatheinternalspeaker.Assoundcards,CD-ROM

games,andthenintegratedmotherboardaudiobecame

ubiquitous,theneedtowritededicatedtimerchipmusicor

kludgesamplesthroughtheinternalbeeperevaporated,and

PCspeakeraudiovanishedfromaudioselectionscreens.

Backtothepresent

Today,PCspeakermusicisn’tasdeadasyoumightexpect.

AlthoughlessiconicthantheC64orNESaudiosystems,you

canhearitsinfluenceinthemodernchiptunesmusicscene.

InFebruary2019,RussiancomposerShirureleased

SystemBeeps,anentirealbumwrittenforthePCspeaker

andusingsomeofthemostsophisticatedarrangement,

arpeggiationandhearingperceptiontrickswe’veheardto

createanillusionofpolyphony.Thereis,ofcourse,a DOS

versionofthealbum,butif youdon’thappentohaveany

classicPChardware(ora copyofDOSBox),it’salsoavailable

tobuyinconventionaldigitalformats.

ShiruusedmodernDigitalAudioWorkstationsoftware

tocomposeSystemBeepsandhasmaderelevantplug-ins,

projectsandsourcecodeavailableforanyoneelsewho

wantstoplaywiththem.

Shiruisn’taloneinworkingonmusiccreationtoolsfor

yourinternalbeeper.BaWaMI,createdbyRobbi-985,is a

WindowsMIDIsynthesiserthatwilloutputviaPCspeaker.If

you’resoinclined,youcanstillhearandmakenewmusicfor

thePC’soldestaudiodevice.

An arpeggiated
pseudo-polyphonic
‘chord’ from
The Secret of
Monkey Island

A classic PC speaker
square wave from
the theme to Space
Quest III: The Pirates
of Pestulon

FURTHER LISTENING

The Secret of Monkey Island

custompc.co.uk/MonkeyIsland

PCM audio through the PC speaker

custompc.co.uk/PCM

Album: System Beeps

custompc.co.uk/SystemBeeps