principles and tools employed by sph for music creation

• avoid post-processing

  • modification of float values can be lossy
  • control as much as possible by initial arguments
  • prefer additive to subtractive processes
• times and offsets are specified in number of samples in cases where hertz and seconds do not map exactly to sample counts
• use wavelengths whose extremes fall exactly on samples
• use a high resolution for processing of modulation. ideally sample resolution
• processing is done for multiple channels with one array per channel
• sample format is variable (32 or 64 bit float, ideally more)
• sample rate is variable (low for fast processing). target sample rate is 96000. a sine of 12000 hz could then still be approximated with 8 samples
• tend to give up realtime processing for higher precision and more content. render to file, which is common in 3d modeling software
• when using random number generators, specify random seeds to keep the output repeatable

• filtered noise generator whose amplitudes and filter values can be controlled by paths. customisable noise generator
• sine generator that keeps a continuous phase when frequency modulated and whose amplitudes and wavelength can be controlled by paths. sine(amp, frq, phs)
• file output with creation of wave files (ideally au, an extremely simple and capable file format)
• random number generator with customisable probabilities

• paths

  • interpolation between points
  • linear and rounded (bezier) interpolation methods
  • segment types are linear, bezier, sub-path or constant

• sequencer

  • for partials and whole songs
  • calls functions that write to sample buffers at specified times
  • called with a time offset, output buffers and an event list
  • sequencer calls can be nested to build composite sounds, patterns and riffs
  • processing can be done in parallel (top-level use) or serial (nested use)

  • event

    • have the properties (state start end function)
    • multiple events can be grouped into one event
    • output can be post-processed
    • output can be cached

• filters

  • windowed-sinc band-pass that optimises to low-pass and high-pass at the edges

  • state-variable filter with low/high/band pass output for cheaper filter operation

  • all filters must be able to filter a series of sample arrays seamlessly

• sph-sp minimal sound synthesis toolkit