Audio

1
Audio

• Audio synthesis
• Sequencing

2
Synthesis

• Analog Synthesis
• Simple sum of frequencies
• Select from a palette of source frequencies
• Sum of frequencies is filtered
• FM
• One frequency is controlled by another
• Wavetable
• Digitize audio signals

3
Wavetable Synthesis

• Collect a sample of the real sound
• Issues
• Reduce memory load by looping sample
• Shift pitch instead of sampling each individual
  note
• Apply interpolation techniques to make pitch
  shifting work right

4
Audio Path
Reverb, Environment. Spatialization
Envelope Loudness Control
Mixing/ Combination
5
Wavetable Synthesis Example

• Leyanda (Guitar)
• Leyanda (CDShaw)

6
Interactive Sound

• Goal
• Want to enhance the interactive experience
• Give the user a sense of presence
• Add to the emotional content of the game
• Make it more fun

7
Interactive Sound

• Music
• Sound effects
• Noises
• Commentary - Sports
• Narrative
• Conversations

8
Interactive Problems

• Regular music composition has
• Beginning
• Middle
• End
• Interactive user control makes this difficult
• Some genres have this structure

9
Interactive Music

• Game genres with order
• Sports
• Racing
• Fighting
• Semi-Ordered
• Puzzle
• Adventure

10
Music Genres

• The Infinite Loop
• Theme and variation plays forever
• Pomp Circumstance
• Diablo
• Problems
• 30 second piece repeated over 6 hours!
• 720 repetitions!
• Diablo example 12 Repetitions/hour

11
Repetition Solutions

• Make the Dominant theme hard to find
• No catchy theme!
• Create a variety of textures
• Make only transitions stand out
• Where repetition is small
• Dont repeat musical phrases

12
Music Strategies

• Play Win or Lose music
• Music must be long enough to be meaningful
• Music may be so long that the game situation
  changes before completion
• Very short music makes little sense
• Interrupt current music
• Sounds jarring

13
Modules

• Modular chunks
• Each segment of the game plays independently of
  others
• Some thematic relation
• Disjointed

14
Music Strategies

• Compose many themes in parallel
• Switch between themes
• Connect modular components together

15
Analogy Parallel Trains

• N trains of music running in parallel
• Each train serves an emotional purpose
• Train A Calm
• Train B Rising Excitement
• Train C Climactic moments
• Train D Falling Excitement
• Generally, Train A would be most commonly played

16
Within Each Musical Train

• Each Car contains a few bars of music
• Switch between trains when a Car is complete
• Dont switch in the middle of a Car
• Simple version
• Each musical phrase ends on last bar of Car
• Complex
• Notes at end are carried over to next

17
Parallel Trains
18
Parallel Trains Shuffle Cars

• Shuffle cars
• Instead of playing cars in order
• Problem Random cars sound like random radio
  tuning
• Must determine
• Appropriate car pairings
• Reasonable paths

19
Repetition In Trains

• Use repeated phrases carefully
• Maybe use a statistical tool to analyze paths
• Bayesian nets
• Endings
• Use transitions as an opportunity to End
• Use next Car to Begin new series

20
Composing a Train

• Create a piece with all layers
• Piece can probably survive a layer or two removed
• Variation piece with layer removed
• Be careful with prominent instruments
• Fallback Use instruments with similar acoustical
  properties
• Piano, Organ, Woodwinds
• No Trumpets, Drums or Screaming guitar!