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Exploring Sound Synthesis and Arithmetic with MIDI and Audacity Techniques

This lecture delves into the fundamentals of sound synthesis and arithmetic through the lens of MIDI (Musical Instrument Digital Interface) and sound editing using Audacity. It covers essential concepts such as pitch, duration, delay, and timbre, while demonstrating how to manipulate MIDI files to transpose notes, change instruments, and vary playback speed. Additionally, it explains sound editing techniques, including amplification, blending, and creating echoes, helping learners understand sound as an array of amplitudes and how to create complex audio compositions from simple sounds.

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Exploring Sound Synthesis and Arithmetic with MIDI and Audacity Techniques

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Presentation Transcript

  1. Lecture # 23 Sound Synthesis & Sound Arithmetic

  2. Jane Fred loves A “sound font” dog loves Fred the Jane Ralph knows

  3. MIDI - Musical Instrument Digital Interface • Object representation of music • Every sound has • Pitch (frequency of the sound) • Delay (how long after last sound start to start playing) • Duration (how long should it play) • Timbre (which instrument should it sound like?) • Guitar • Clarinet • Violin

  4. A MIDI file • An array of notes 0 (262, 0,10,1) 1 (300, 10,10,1) 2 (262, 10, 10, 1) 3 (300, 0, 10, 1) Delay Pitch (middle C) Duration Instrument Number During performance numbers are assigned to different instruments

  5. MIDI demo http://www.free-midi.org/midi1/v/vangelis-chariots_of_fire.mid

  6. A MIDI file • An array of notes 0 (262, 0,10,1) 1 (300, 10,10,1) 2 (262, 10, 10, 1) 3 (300, 0, 10, 1) How do we transpose to a higher key? Increase pitch of each note

  7. A MIDI file • An array of notes 0 (262, 0,10,1) 1 (300, 10,10,1) 2 (262, 10, 10, 1) 3 (300, 0, 10, 1) How do we make it play faster? Reduce delay and duration of each note

  8. A MIDI file • An array of notes 0 (262, 0,10,1) 1 (300, 10,10,1) 2 (262, 10, 10, 1) 3 (300, 0, 10, 1) How do we change from guitar to flute? Assign a different instrument to that number

  9. Synthesizing an instrument • Mix different harmonics • Add noise • Adjust Attack, Dwell, Sustain, Release

  10. Synthesizing an Instrument • Attack - when string is plucked or note is struck • Dwell - energy left from attack • Sustain - while the note is held • Release - after player stops

  11. Synthesizing an Instrument • Attack - when string is plucked or note is struck • Dwell - energy left from attack • Sustain - while the note is held • Release - after player stops

  12. Synthesizing an Instrument • Attack - when string is plucked or note is struck • Dwell - energy left from attack • Sustain - while the note is held • Release - after player stops

  13. Synthesizing an Instrument • Attack - when string is plucked or note is struck • Dwell - energy left from attack • Sustain - while the note is held • Release - after player stops

  14. Synthesizing an Instrument • Attack - when string is plucked or note is struck • Dwell - energy left from attack • Sustain - while the note is held • Release - after player stops

  15. Sampled / Object Sampled Object Jane loves Fred

  16. Sound Editing and Processingwith Audacity

  17. Edit Sound • Drag and Drop (universities-deep_thoughts.wav) • File >> Import >> Audio • Notice new track (two if it is stereo) • File >> Import >> Audio (theknack.wav) • Notice second track • Select Track • Select Time Shift action • Move Track • Mix and Render (“barnyard”: cow, horse, duck) • Play/Mute/Align • Undo (Cntrl-Z)

  18. Edit Sound • Split • Align • Select All • Import Dance Music • Trim • Shape • Record • Sing a round/Play around • Amplify/Distort • Blend • Arithmetic with Sounds

  19. Arithmetic on Sound • Sound is an array of amplitudes (numbers) • The higher the amplitude, the louder the sound • Adding two sounds together • Make a sound louder or softer • Blends of two sounds • Echos

  20. Adding two sounds Laser Guns + Distress = New Sound

  21. Adding two sounds Algorithm Laser = laser gun sound; Warn = warning message; NewSnd = new array(Laser.length); for (each index i in NewSnd) { NewSnd[i]=Laser[i]+Warn[i]; }

  22. Adding Sounds Demo • Drag or manufacture 2 or more track • Play • Shift • Mix and Render

  23. Making a sound louder

  24. Amplify Sound Demo • Effects -> Amplify

  25. Making a sound louder for (each index i in oldSound) { newSound[i]=oldSound[i]*3; }

  26. General Amplify algorithm amp = 3.0; three times as loud for (each index i in oldSound) { newSound[i]=oldSound[i]*amp; }

  27. General Amplify algorithm amp = 0.5; half as loud for (each index i in oldSound) { newSound[i]=oldSound[i]*amp; }

  28. Blending two sounds Music 50% music, 50% words Words

  29. Blending Sounds Demo • 2+ Tracks -> Effects -> Amplify • Tracks -> Mix Render

  30. Algorithm for Blending two sounds B = blend value between 0.0 and 1.0 for (each index i in Snd1) { newSnd[i]=(1.0-B)*Snd1[i]+ B*Snd2[i]; }

  31. Singing a Round by yourself • Row Row Row your boat • Sing in a round

  32. Singing a round by yourself + Time delay =

  33. Singing a round by yourself Demo • 2+ tracks -> align/shift/paste • Tracks -> Mix Render

  34. Singing a round by yourself song = the original song; delay = how many samples to delay; newSng = new array(song.length+delay); for (each index i in song) { newSng[i] = song[i]; } for (each index i in song) { newSng[i+delay] = newSng[i+delay]+song[i]; }

  35. Echoes • An echo occurs because sound returns delayed and softer after bouncing off of something • Original • Canyon Echo (large delay) • Room Reverb (small delay)

  36. Echoes Demo • Audacity • Effects -> Echo

  37. Echoes Algorithm sound = the original sound; delay = how many samples to delay; softness = 0.1; newSound = new array(sound.length+delay); for (each index i in sound) { newSound[i] = sound[i]; } for (each index i in sound) { newSound[i+delay] = newSound[i+delay] + sound[i]*softness; }

  38. Review • Sound Synthesis (MIDI, timbre, pitch, etc) • Change Pitch • Change Tempo • Change Speed

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