sfplay — Plays a SoundFont2 (SF2) sample preset, generating a stereo sound.
Plays a SoundFont2 (SF2) sample preset, generating a stereo sound. These opcodes allow management the sample-structure of SF2 files. In order to understand the usage of these opcodes, the user must have some knowledge of the SF2 format, so a brief description of this format can be found in the SoundFont2 File Format section.
ivel -- velocity value
inotenum -- MIDI note number value
ipreindex -- preset index
iflag (optional) -- flag regarding the behavior of xfreq and inotenum
ioffset (optional) -- start playing at offset, in samples.
ienv (optional) -- enables and determines amplitude envelope. 0 = no envelope, 1 = linear attack and decay, 2 = linear attack, exponential decay (see below). Default = 0.
xamp -- amplitude correction factor
xfreq -- frequency value or frequency multiplier, depending by iflag. When iflag = 0, xfreq is a multiplier of a the default frequency, assigned by SF2 preset to the inotenum value. When iflag = 1, xfreq is the absolute frequency of the output sound, in Hz. Default is 0.
When iflag = 0, inotenum sets the frequency of the output according to the MIDI note number used, and xfreq is used as a multiplier. When iflag = 1, the frequency of the output, is set directly by xfreq. This allows the user to use any kind of micro-tuning based scales. However, this method is designed to work correctly only with presets tuned to the default equal temperament. Attempts to use this method with a preset already having non-standard tunings, or with drum-kit-based presets, could give unexpected results.
Adjustment of the amplitude can be done by varying the xamp argument, which acts as a multiplier.
Notice that both xamp and xfreq can use k-rate as well as a-rate signals. Both arguments must use variables of the same rate, or sfplay will not work correctly. ipreindex must contain the number of a previously assigned preset, or Csound will crash.
The ioffset parameter allows the sound to start from a sample different than the first one. The user should make sure that its value is within the length of the specific sound. Otherwise, Csound will probably crash.
The ienv parameter enables and determines the type of amplitude envelope used. The default value is 0, or no envelope. If ienv is set to 1, the attack and decay portions are linear. If set to 2, the attack is linear and the decay is exponential. The release portion of the envelope has not yet been implemented.
sfplay plays a preset, generating a stereo sound. ivel does not directly affect the amplitude of the output, but informs sfplay about which sample should be chosen in multi-sample, velocity-split presets.
These opcodes only support the sample structure of SF2 files. The modulator structure of the SoundFont2 format is not supported in Csound. Any modulation or processing to the sample data is left to the Csound user, bypassing all restrictions forced by the SF2 standard.