EE2F2 – Music Technology

1. EE2F2 – Music Technology Dr. Tim Collins T.Collins@bham.ac.uk www.eee.bham.ac.uk/collinst/music

2. Introduction • Course content: • How modern technology is used by musicians • Recording studio technology: • Multi-track recording and mixing • Effects processing • Computerisation • Performance technologies: • Electric instruments • Synthesisers and Samplers

3. A Brief History

4. Recording Technology • Simplest scenario – single microphone, recorded straight to tape. • More common – several performers recorded separately and then mixed together later. • We will look at the key elements in the audio signal chain: • Microphones / electronic instruments • Mixers • Multi-track tape recorders • Effects • We will also look at the use of computers for MIDI sequencing, and digital audio.

5. The Audio Signal Chain • The audio signal chain contains all the steps between the original performance and the final distribution. Mastering Mics and electronic sources Track laying mixer Multi-track recorder Mixdown to stereo Stereo recorder

6. Multi-track Recording • These days, music is rarely recorded in one ‘take’ except for: • Live performances • Classical music • Usually, songs are built-up from several parts using a multi-track recorder • A multi-track recorder can • Record lots of separate sounds independently • Play them all back at once

7. Drums Bass Guitar Piano Flute Four-Track Example Track 1 - Blank Track 2 - Blank Track 3 - Blank Track 4 - Blank

8. Audio Signal Chain Components • Over the next few weeks we will look at the audio signal chain in more detail. In particular: • Microphones • Mixing • Multi-Track Recording • Mastering • Computerisation and Automation Mastering Mics and electronic sources Track laying mixer Multi-track recorder Mixdown to stereo Stereo recorder

9. Microphones • Microphones are transducers that convert acoustical energy (i.e. mechanical vibration) into electrical energy. • Two main types used for music: • Electromagnetic: Dynamic and ribbon designs, work by electromagnetic induction. • Capacitor: Condenser design, works by changing the shape of a charged capacitor.

10. Audio output Fixed earth plate d.c. bias voltage Diaphragm Condenser (or capacitor) Microphone Diaphragm moves due to sound waves Capacitance and thus voltage change Microphones • Regardless of the mechanism, important parameters are: • Frequency response • Sensitivity • Directional response Diaphragm Magnet Coil Dynamic Microphone Diaphragm and coil move due to sound waves Current is induced in coil

11. Example - Shure SM58 Dynamic (moving coil) microphone popularly used for vocals. Sensitivity = -54.5 dBV/Pa (2.8 mV/Pa)

12. Signal Levels • Even the most sensitive microphones have sensitivities no higher than around 10 mV/Pa. • When held close to the mouth of a singer, a typical sound pressure will be around 1 Pascal. • So, even the most sensitive microphone will produce a signal of around 10 mV in amplitude. • Typically, for common microphones, the signal level would be around 1 mV (depending on how loud the singer is and on the microphone positioning).

13. Mixing Frequently Asked Question: “What do all those knobs do ?”

14. Mixers • In the simplest terms, all a mixer does is to add together two or more input voltages. • In practice, it must also provide gain controls in order to: • Correctly mix signals from different sources, e.g. • Line level signals (~1 V) from electronic instruments • Mic level signals (~1 mV) from microphones • Balance the different parts of a mix. • Actually, most mixers perform several other functions as well. We will cover them in a later session.

15. Tape Recorders • There are two types of tape recorder in the audio signal chain. • Stereo (two track) recorders, similar to domestic hi-fi tape decks. • Multi-track recorders (anything from 4 to 24 tracks) • Analogue and digital versions of both types are available. • These days, mostly digital machines are used. • In fact, magnetic tape is often not used at all. Hard disk recording is becoming more common.

16. Mastering • The master tape containing the final stereo mix must be duplicated in different ways for different distribution media. • Vinyl LPs require special equalisation (filtering) • Cassette masters are made on special tape used for high speed duplication • CDs require the addition of codes to mark the start and end of tracks • These processes are known as mastering.

17. Computerisation & Automation • Computers have been gradually introduced into the recording studio to automate certain tasks: • Triggering drum machines with preset patterns (sequencing) • Changing fader levels on a mixing desk to preset levels at the right time • Triggering (remotely playing) electronic instruments (via MIDI) • Digitally recording onto hard disk • Generating synthetic sounds using software synthesisers • Generating special effects in software • Replacing most of the equipment in a conventional studio with virtual software equivalents

18. Summary • In this course, we will be looking at how modern technology has affected musicians in terms of: • Recording technology • Synthesis and sampling technology • The basis of most contemporary recordings is the multi-track concept. • This is traditionally realised using analogue multi-track tape machines. • Nowadays it is often done digitally in software. • Next time: Stereo and Multi-track recording