Instrument Design

RTcmix provides a set of C/C++ functions and objects for constructing new signal-processing and synthesis instruments. The source code for most of these low-level routines are in the “RTcmix/lib” and “RTcmix/sys” subdirectories of the RTcmix distribution.

In addition to the reference material below, a tutorial is available for creating and compiling RTcmix instruments.

Arrange by: Topic · Alphabetical

Processing Control/Sound Input & Output

Instrument – base class for all RTcmix instruments; contains many essential functions and variables
- configure – designer-overridden virtual function to configure an RTcmix instrument
- currentFrame – return current sample frame #
- framesToRun – return number of frames to run for each Instrument::run() invocation
- getdur – returns duration (seconds) of the note
- getendsamp – returns the (absolute) ending sample # (frame) for a note
- getSkip – returns the number of samples in one control (reset) period
- getstart – returns starting time (seconds) of the note
- increment – update the computed-sample count
- init – designer-overridden virtual function to initialize an RTcmix instrument
- inputChannels – return the number of input channels
- nSamps – return total number of frames (samples) to run for a note
- outputChannels – return the number of output channels
- run – designer-overridden virtual function for computing samples
- setchunk – sets the number of sample frames computed for each Instrument::run() invocation
- setendsamp – sets the (absolute) ending sample # (frame) for a note
Obucket – internally buffer samples or floating-point numbers
Ortgetin – read input samples from file or input device
rtaddout – send samples to the output device or soundfile
rtbaddout – send an array of samples to the output device or soundfile
rtgetin – get samples from the input device or soundfile
rtinrepos – reposition the input read pointer
rtsetinput – open and initialize a soundfile or input device for reading
rtsetoutput – open and initialize the output device and/or soundfile for writing
update – retrieve PField-handle or table-handle data

Synthesis

Ooscil – non-interpolating wavetable oscillator object; also can be used for control envelopes
Ooscili – interpolating wavetable oscillator object; also can be used for control envelopes
oscil – wavetable oscillator
oscili – interpolating wavetable oscillator
osciln – wavetable oscillator (FM-compatible)
oscilni – interpolating wavetable oscillator (FM-compatible)
boscili – block-computing interpolating wavetable oscillator
buzz – buzz (pulse) oscillator
bbuzz – block-computing buzz (pulse) oscillator
pluckset – simple Karplus-Strong (“plucked string”) initialization
pluck – simple Karplus-Strong (“plucked string”) filter/generator
bpluck – some sort of Karplus-Strong thing
hplset – Karplus-Strong (“plucked string”) initialization
hpluck – Karplus-Strong (“plucked string”) filter/generator
wshape – waveshaping function

Math/Data

ampdb – convert decibels to amplitude
dbamp – convert amplitude to decibels
boost – convert amplitude in decibels to amplitude multiplier

Pitch-specification Conversion Routines

cpsoct – convert linear octaves to Hz
cpspch – convert octave.pitch-class to Hz
midipch – convert Hz to midi note #
octcps – convert Hz to linear octaves
octpch – convert octave.pitch-class to linear octaves
pchcps – convert Hz to octave.pitch-class
pchmidi – convert midi note # (byte) to frequency (Hz)
pchoct – convert linear octaves to octave.pitch-class

Random-Number Routines

Orand – pseudo-random number generating object
crandom – another psuedo-random number generator
randf – 1/f pseudo-random number generator(?)
srrand – pseudo-random number generator seed/initialization
rrand – pseudo-random number generator
sbrrand – block-computed pseudo-random number generator seed/initialization
brrand – block-computed pseudo-random number generator

Function-table Slot Operations

floc – return a pointer to a function table slot
fsize – return the size of a function table slot array
evset – envelope/control function initialization
evp – envelope/control function generator
install_gen – install a function table slot from within an instrument
combine_gens – combine function tabbles
resample_gen – resample a function table
setline – create line-segment curve in an array
tableset – initialize a function table slot for envelopes/control functions
table – read from a function table slot for envelopes/control functions
tablei – interpolated read from a function table slot for envelopes/control functions

Filters

Ocomb – comb filter object
Ocombi – interpolating comb filter object
Odcblock – DC blocking filter object
Oequalizer – multi-purpose biquad filter object
Oonepole – simple recursive one-pole filter object
OonepoleTrack – simple ‘tracking’ recursive one-pole filter object
Oreson – simple recursive bandpass filter object
allpass – allpass filter
allpole – allpole filter
ballpole – block-computing allpole filter
rsnset – two-pole FIR filter initialization
reson – simple two-pole FIR filter
breson – block-computed two-pole FIR filter
bresonz – block-computed two-pole FIR filter
rszset – simple IIR filter initialization
resonz – simple IIR filter

Delays

Odelay – delay line object
Odelayi – interpolating delay line object
combset – comb filter setup function
comb – comb filter
hcomb – interpolating comb filter
delset – initialize a delay line
delput – put a sample into a delay line
delget – get a sample from a delay line
dliget – get an interpolated sample from a delay line
rvbset – initialize poor-quality reverb
reverb – poor-quality reverb

Other

Offt – FFT analysis object

Disk-based (non-realtime) Functions

There are a number of older ‘disk-only’ sound synthesis and signal-processing functions that may be encountered in instrument design. These were originally developed for the non-realtime cmix music programming language from which RTcmix was derived. RTcmix actually encapsulates all of the earlier cmix code, so that these funcions that have not been ported to RTcmix still work. We include documentation for these older disk-based functions mainly for those compelling “historical” reasons, because none of them will access the real-time audio stream of sound.

ADDOUT – add samples to disk
GETIN – get samples from disk
LAYOUT – write samples selectively to disk
WIPEOUT – write samples destructively to disk
baddout – add a block of samples to disk
bgetin – get a block of samples from disk
blayout – write a block of samples selectively to disk
bwipeout – write a block of samples destructively to disk
endnote – update file header statistics at end of note
getsample – fetch arbitrary block of samples from soundfile
getsetnote – set up for getsample()
inrepos – reposition the input file pointer
outrepos – reposition the output file pointer
setnote – set up soundfile for reading/writing