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TA212 The Technology of Music

TA212 The Technology of Music. Steve Wells. Tutorial 4. TMA04 cutoff date January 22nd Block 4 Part 1 starts February 15th. Tutorial 4. TMA04 cutoff date January 22nd Block 4 Part 1 starts February 15th. Block 4 Part 1 doesn’t start until February 15 th ...

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TA212 The Technology of Music

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  1. TA212The Technology of Music Steve Wells

  2. Tutorial 4 • TMA04 • cutoff date January 22nd • Block 4 Part 1 • starts February 15th TA212 The Technology of Music

  3. Tutorial 4 • TMA04 • cutoff date January 22nd • Block 4 Part 1 • starts February 15th Block 4 Part 1 doesn’t start until February 15th... but we don’t have another tutorial until April 12th... ! TA212 The Technology of Music

  4. TMA04 • Question 1 – Basics of Instruments • vibrators, percussion, damping • calculations based on vibrating plate • Question 2 - Clarinet • reed, transposition • frequency analysis in Audition TA212 The Technology of Music

  5. TMA04 • Question 3 - Brass instruments • mouthpiece, bell, mute, valve • Question 4 - Violin • bow, bridge • calculations based on strings TA212 The Technology of Music

  6. Calculations in TMAs • ALWAYS quote any formula you are using • ALWAYS define the terms in the formula • f1: fundamental frequency (Hz) • L: length of the string (m) • T: tension in the string (N) • µ: mass per unit length (kg/m) TA212 The Technology of Music

  7. Calculations in TMAs • Save any rounding of results until the end • Rounding of intermediate results leads to errors • Example from TMA03 To get the peak to peak we need: This is the rms voltage. TA212 The Technology of Music

  8. Calculations in TMAs • Save any rounding of results until the end • Rounding of intermediate results leads to errors • Example from TMA03 To get the peak to peak we need: This is the rms voltage. TA212 The Technology of Music

  9. Block 4: Sound Processes Desktop Sound Notation and Representation Carillon to MIDI Music Distribution The Music Business TA212 The Technology of Music

  10. Block 4: Sound Processes Desktop Sound Notation and Representation Carillon to MIDI Music Distribution The Music Business TA212 The Technology of Music

  11. Desktop Sound TA212: Block 4, Chapter 1

  12. Three Stages • Collect the sound • Edit, Mix and Add Effects • Distribute the Result • The three stages are sometimes marked on CDs to show whether analogue or digital technology was used at each stage: A D D D D D TA212 - Block 4 - Chapter 1 - Desktop Sound

  13. Analogue Input - Sensitivity • Signal Amplitude • High Sensitivity • microphones etc. • Low Sensitivity (“Line”) • synthesisers etc. TA212 - Block 4 - Chapter 1 - Desktop Sound

  14. Specifying Sensitivity (revision) RMS amplitude is the amplitude equivalent to a non oscillating source carrying the same power. amplitude rms amplitude peak to peak amplitude TA212 - Block 4 - Chapter 1 - Desktop Sound

  15. Decibels (again!) • Think of voltages and power as analogues of sound • Sound level is measured in dB - so can voltages and power • Need to define the zero point • 0dBu is defined as an rms voltage of 0.775 volts • 0dbV is defined as an rms voltage of 1 volt • 0dBm is defined as a power of 1 mW TA212 - Block 4 - Chapter 1 - Desktop Sound

  16. Decibels – standard values • - 20dB one tenth of the voltage/power • + 20dB ten times the voltage/power • - 6dB half the voltage/power • + 6dB twice the voltage/power TA212 - Block 4 - Chapter 1 - Desktop Sound

  17. Impedance (revision) • Equivalent of electrical resistance for an oscillating signal • Varies with frequency • but this is usually not specified • Impedance matching • Get it wrong and you lose power TA212 - Block 4 - Chapter 1 - Desktop Sound

  18. Impedance Matching low  high high low  very high high low high Pre-amplifier TA212 - Block 4 - Chapter 1 - Desktop Sound

  19. Analogue Output - Clipping • The clipped signal has been amplified too much and the extremes of the amplitude have been lost • Very unpleasant sound! TA212 - Block 4 - Chapter 1 - Desktop Sound

  20. TRS Connector Tip Insulation to separate the connections Ring Sleeve TA212 - Block 4 - Chapter 1 – Desktop Sound

  21. 3.5mm TRS Connector Speakers Left Channel Right Channel Ground (0v) TA212 - Block 4 - Chapter 1 – Desktop Sound

  22. 3.5mm TRS Connector Speakers Microphone Left Channel Signal Right Channel Preamp Power (5v) Ground (0v) Ground (0v) For high impedance microphones (such as electrets), 5 volts is supplied to the microphone to drive an in-built preamplifier TA212 - Block 4 - Chapter 1 – Desktop Sound

  23. Cables • screened leads • balanced leads signal wire earth two signal wires twisted together earth TA212 - Block 4 - Chapter 1 - Desktop Sound

  24. Balanced Cables TA212 - Block 4 - Chapter 1 - Desktop Sound

  25. Digital Interfaces • Standards • AES/ABU • S/PDIF • MADI • Essentially the same! • Serial transmission • one bit at a time • Real Time • USB and Firewire also used on desktop systems TA212 - Block 4 - Chapter 1 - Desktop Sound

  26. Digital Storage • Compact Disc (CD) • MiniDisc (MD) • Digital Versatile Disc (DVD) • Magnetic Tape • Hard Disk • Solid State memory TA212 - Block 4 - Chapter 1 - Desktop Sound

  27. Digital Storage Issues • What stage of the recording process? • Initial Recording • high capacity required • Magnetic Tape or Hard disk • Digital Mixing • Random Access • Hard Disk • Delivery • CD etc. TA212 - Block 4 - Chapter 1 - Desktop Sound

  28. Digital File Formats • All have basically the same structure • based on “Interchange File Format” (IFF) • Built from “chunks” • All chunks consist of • identity • size • data • The data part of a chunk can contain other chunks. TA212 - Block 4 - Chapter 1 - Desktop Sound

  29. Chunk Structure Identity 4 bytes Size 4 bytes Data Size bytes TA212 - Block 4 - Chapter 1 - Desktop Sound

  30. WAV File “RIFF” 4 bytes Size 4 bytes “WAVE” Format Chunk Data Chunk Size bytes TA212 - Block 4 - Chapter 1 - Desktop Sound

  31. WAV Format Chunk “FMT ” Size • Format of data • number of tracks • sample rate • etc. Sound Parameters TA212 - Block 4 - Chapter 1 - Desktop Sound

  32. WAV Data Chunk “DATA” Size • Actual Sound Samples Sound Samples TA212 - Block 4 - Chapter 1 - Desktop Sound

  33. Editing • Combining many sound sources to produce a single stereo image which can be recorded to CD • adjustment of levels • mixing different takes to remove imperfections • adding effects • Edit Lists • Non-Destructive • real time TA212 - Block 4 - Chapter 1 - Desktop Sound

  34. Setting the Levels • Normalisation • Setting the final levels based on the loudest part of the recording • Setting the levels to -6dB means setting the loudest part of the recording to 6dB below clipping. • Compression and Limiting • Reduce the output level when the input level is high • Reduces the dynamic range • Expansion and Gating • Increase the output level when the input level is low • Reduces the dynamic range TA212 - Block 4 - Chapter 1 - Desktop Sound

  35. Mixing • During recording several microphones are used to record individual performers or groups • Mixing is the process of combining these individual recordings • Adjusting the levels of individual tracks TA212 - Block 4 - Chapter 1 - Desktop Sound

  36. Controlling the Level • analogue signals when added can produce clipping • digital signals run out of space! • two 16 bit samples when added will require 17 bits. • two approaches • increase the capacity in the mixing stage • reduce the sample sizes (downsizing) • a 1 bit reduction halves the sample value TA212 - Block 4 - Chapter 1 - Desktop Sound

  37. Carillon to MIDI TA212: Block 4, Chapter 3

  38. What is MIDI? • Musical Instrument Digital Interface • a way to carry information about music from one place to another along a wire or in a file • which note to play • when to start • which instrument to use TA212 - Block 4 - Chapter 3 - Carillon to MIDI

  39. MIDI Connections MIDI In MIDI Thru Synthesiser “local off” switch MIDI Out TA212 - Block 4 - Chapter 3 - Carillon to MIDI

  40. MIDI Messages • Instructions about what sounds to make • Status byte • note on • note off • program change (new instrument) • Data byte(s) • numerical information • pitch, volume etc. TA212 - Block 4 - Chapter 3 - Carillon to MIDI

  41. MIDI Channels • MIDI can support 16 channels. Each can be a separate synthesised instrument • Status bytes which refer to channels are arranged in blocks of 16 • So... • 144: “Note On” on Channel 1 • 145: “Note On” on Channel 2 • etc. TA212 - Block 4 - Chapter 3 - Carillon to MIDI

  42. MIDI Example 145 60 64 129 60 64 Note On - Channel 2 Middle C (C4) Mid range velocity (loudness) Note Off - Channel 2 Middle C (C4) Mid range velocity (loudness) TA212 - Block 4 - Chapter 3 - Carillon to MIDI

  43. Running Status • When repeating a message with the same status as the last message • just send the data • the status is implied • Don’t need to use NOTE OFF - just use NOTE ON again with a velocity of 0 • With a lot of notes this can save a lot of status bytes. TA212 - Block 4 - Chapter 3 - Carillon to MIDI

  44. Running Status Example • Without running status: • 146, 60, 64, 146, 64,64, 130, 60, 64, 130, 64, 64 • With running status: • 146, 60, 64, 64,64, 130, 60, 64, 64, 64 Repeated status bytes Repeated status bytes removed TA212 - Block 4 - Chapter 3 - Carillon to MIDI

  45. MIDI File • Standard MIDI File uses the Interchange File Format • like a WAV file • Fixed size Header Chunk • One Track Chunk per MIDI Track TA212 - Block 4 - Chapter 3 - Carillon to MIDI

  46. SMF Header Chunk “MThd” 4 bytes 0: One Track 1: Many tracks played together 2: Many tracks played in sequence Size (always 6 bytes) 4 bytes Format type 2 bytes No. of Tracks 2 bytes Time 2 bytes +ve: number of clock ticks per crotchet -ve: number of ticks between SMPTE Time Frames TA212 - Block 4 - Chapter 3 - Carillon to MIDI

  47. SMF Track Chunk • One Chunk per Track • Each MIDI Event consists of: • Delta Time • MIDI Message • Status Byte • Data Bytes “MTrk” Size MIDI Events TA212 - Block 4 - Chapter 3 - Carillon to MIDI

  48. Contacting Me • Phone 01454-850379 • Email s.wells@.open.ac.uk • Web http://www.stevesphotosite.co.uk/ta212 TA212 The Technology of Music

  49. Questions ? ? ? ? ? ? ? TA212 The Technology of Music

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