anchor.diff:  of the metronome, Afterglow takes a _snapshot_ of the metronome at the
   start of the frame, and the oscillators work from that.
   
  -[[sawtooth-oscillators]]
  -Sawtooth Oscillators
  -~~~~~~~~~~~~~~~~~~~~
  -
  -code,clojure--------------------------------------------- code,clojure
  +== Sawtooth Oscillators
  +
  +[source,clojure]
  +----
   (afterglow.effects.oscillators/sawtooth-beat)
  ----------------------------------------------
  +----
   
   Returns an oscillator which generates a
   http://en.wikipedia.org/wiki/Sawtooth_wave[sawtooth wave] relative to
  
positive.code: Oscillators in Afterglow are a flexible way of turning the timing
  information tracked by [[metronomes|metronomes]] into waveforms that can
  be used to make lights do interesting things. They can be related to the
  beats, bars, or phrases of the metronome, or multiples or fractions
  thereof, and can create link:#sawtooth-oscillators[sawtooth],
  link:#triangle-oscillators[triangle], link:#square-oscillators[square],
  or link:#sine-oscillators[sine] waves.
  
  Metronomes keep track of musical time relative to some starting point,
  in terms of beats, bars (by default four beats to a bar), and phrases
  
negative.code: interval.
  
  So, in a sense, by itself a metronome can give you a
  <<#sawtooth-oscillators,sawtooth>> wave related to its intervals, just
  by looking at the interval phase. The sawtooth oscillators build on that
  by letting you change the direction of oscillation, so it starts at 1.0
  and slides downward, the speed of oscillation, so it ramps over
  