TA212 The Technology of Music Steve Wells

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

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

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

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

Calculations in TMAs ALWAYS quote any formula you are using ALWAYS define the terms in the formula TA212 The Technology of Music f 1 : fundamental frequency (Hz) L: length of the string (m) T: tension in the string (N) µ: mass per unit length (kg/m)

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

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

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

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

Desktop Sound TA212: Block 4, Chapter 1

TA212 - Block 4 - Chapter 1 - Desktop Sound 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 DD D D

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

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

TA212 - Block 4 - Chapter 1 - Desktop Sound 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 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 Decibels – standard values - 20dBone tenth of the voltage/power + 20dBten times the voltage/power - 6dBhalf the voltage/power + 6dBtwice the voltage/power

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

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

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

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

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

3.5mm TRS Connector TA212 - Block 4 - Chapter 1 – Desktop Sound SpeakersMicrophone Left Channel Right Channel Ground (0v) Preamp Power (5v) Signal 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 Cables screened leads balanced leads signal wire earth two signal wires twisted together

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

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

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

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

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

TA212 - Block 4 - Chapter 1 - Desktop Sound 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 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

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

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

Carillon to MIDI TA212: Block 4, Chapter 3

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

TA212 - Block 4 - Chapter 3 - Carillon to MIDI 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 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 MIDI Example Note On - Channel 2 Middle C (C 4 ) Mid range velocity (loudness) Note Off - Channel 2 Middle C (C 4 ) Mid range velocity (loudness)

TA212 - Block 4 - Chapter 3 - Carillon to MIDI 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 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 Running Status Example Repeated status bytes Repeated status bytes removed

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

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

TA212 The Technology of Music Contacting Me Phone Web

TA212 The Technology of Music Questions ? ? ? ? ? ? ?