A-level Computing/AQA/Problem Solving, Programming, Data Representation and Practical Exercise/Fundamentals of Data Representation/Sound synthesis

Nyquist-theorem Streaming audio thumb|200px|center|Fairlight CMI series II – an early digital synthesiser Sound synthesis Electronically generated sounds that mimic musical instruments or the human voice Sound Synthesisers are also used to create electronic sounds, unknown in the traditional music scene. In 1951 the University of Manchester created the earliest example of computer generated music using the Ferranti Mark 1 computer. Since then computers have had a massive impact on the music industry and this section will look into sound synthesis. CMajor_Chord_in_Different_Instruments.ogg center CMajor chord using different synthesised instruments La_Bandera_de_las_Estrellas.ogg center The Star Spangled Banner sung by the Festival speech synthesis system Sound Synthesis generally creates smaller file sizes compared to recordings taken from live recordings such as MP3 and AAC as it records notation which the computer performs using a selection of programmed or digital instruments, rather than recording the wave forms of each second of sound. However, the recordings often don't sound as real as the live recordings. Listen to the music on the left to see what I mean. thumb|center|MIDI connectors and a MIDI cable A common means to produce sound synthesised music is by using MIDI. MIDI does not record analogue sound, but send digital signals recording musical notation, pitch and intensity, control signals for parameters such as volume, vibrato and panning, cues, and clock signals to set the tempo. The computer then interprets these commands and outputs sound corresponding to them. MIDI is a popular way to record music from devices such as electronic keyboards. Extension: Creating a Sound Synthesiser As we know each character on our keyboard has an ASCII code attached to it. We are going to take this code and turn our computer keyboard into a musical keyboard! console.beep(frequency,duration) Where frequency is the number of oscillations per second and duration is the length that the beep will last in milliseconds. AscW(key) Where AscW is the ASCII number of key pressed. Giving us: Dim duration As Integer = 200 Dim frequency As Integer Dim key As String 'stores the numeric ASCII value Console.WriteLine("press any key to play music, press q to quit") Do key = Console.ReadKey().KeyChar 'get the numeric ASCII value input frequency = (AscW(key) + 50) * 50 Console.Beep(frequency, duration) Loop Until key = "q" To extend this try to add the following: + - increase and decrease frequency = _ increase and decrease duration of sound Exercise: Sound synthesis Why might you prefer to use sound synthesis over recording an orchestra Sound synthesis produces smaller file sizes without loss of quality Sound synthesis allows for easy editing of files after they have been recorded Sound synthesis allows for sounds that would be unachievable using traditional instruments Why might you not want to use sound synthesis Sound synthesis struggles to recreate the sounds made by traditional instruments Sound synthesis struggles to recreate the human voice