Amusicalinstrumentisadeviceconstructedormodifiedwiththepurposeofmakingmusic.Inprincipleanythingthat,producessound,andcansomehowbecontrolledbyapersonplayingit,canserveasamusicalinstrument.Theexpression,however,isreservedgenerallyforitemsthathaveaspecificmusicalpurpose.Theacademicstudyofmusicalinstrumentsiscalledorganology.

　　Voice,thatis,thehumanvoice,isaninstrumentinitsownright.Asingergeneratessoundswhenairflowfromthelungssetsthevocalcordsintooscillation.Thefundamentalfrequencyiscontrolledbythetensionofthevocalcordsandthetonequalitybytheformationofthevocaltract;awiderangeofsoundscanbecreated.

　　Stringinstrumentsgenerateasoundwhenthestringisplucked,strummed,slapped,etc.Thefrequencyofthewavegenerated(andthereforethenoteproduced)usuallydependsonthelengthofthevibratingportionofthestring,itslineardensity(massperunitlengthofstring),thetensionofeachstringandthepointatwhichthestringisexcited;thetonequalityvarieswiththeconstructionoftheresonatingcavity.Examples:guitars,violinsandsitars.