Additive Synthesis tools in SNDAN

for an. format files:

addsyn    addsyn1   addsyn2   addsyn3

NB the addsyn programs do not currently resynthesise 'full' format analysis files reliably.

for .mq format files:

mqsyn2

(see also mqtoan, to convert  .mq files into .an files)

Common parameters

Several parameters and flags are common to all the addsyn programs:

 
• -f
write floating-point samples. See File Formats  for more infomation on the soundfile formats supported by SNDAN.
• -i
read  parameters interactively. This corresponds to the original behaviour of the program, in which any numeric parameters (which are not optional; they are printed in italic in this documentation) not entered on the command line are requested interactively, as a single group. They can also be read from a text file using 'redirection' (see Using the Windows Console). When run in this way the programs print useful information from the header, which can guide the choice of parameter values.

There are nevertheless advantages to the requirement for a complete command line. If a parameter is omitted, the program terminates, rather than present a prompt. This is safer behaviour when the program is run from a batch file (the program will return an error value that can be tested by the batch file). If a parameter is incorrect, the program terminates with an informative message, but as all the parameters were entered into a running program, the MSDOS command-line history command doskey cannot be used to recall the full command line, so that all parameters have to be re-entered. The non-interactive mode is therfore quicker to use; if an error is made the full command line can be retrieved using doskey, and a correction quickly made.
(See Using the Windows Console  for information on doskey).
 
 

• -x
perform byte-swapping for .fp and .sh formats.
• infile
 the input analysis file, in the appropriate format
• outfile
the output soundfile, in one of the supported formats
• sr
sample rate for the outfile (Hz).
As the data in the analysis file is in principle independent of sample rate, you are free to resynthsize using any sample rate. If the chosen rate is lower than that of the original source, the number of harmonics retained will be reduced to avoid aliasing.
• f1
the fundamental frequency for the outfile (Hz).
For an exact reproduction of the source, use the  'Analysis Frequency' given in the analysis file header (run the program interactively to see this, or use showhdr).
By using a lower or higher value, the sound is pitch-shifted down or up. To shift an exact musical interval, some simple arithmetic is needed to find the required frequency. See Pitch Table for a list of frequency ratios for common musical intervals.
• nhar
the number of harmonics to retain in the synthesis.
The number of harmonics available is shown in the analysis file header. You can use a lower number to eliminate higher partials, thus performing simple low-pass filtering (remembering that the partials can rise in pitch - this behaviour is not affected by the nhar setting). Also, where the number of source harmoncis is high (low Analysis Frequency), using a lower value for nhar will spped up processing. Use a low value to confirm the general quality of the analysis, or to check the effect of other parameters.  Then use more, or all, harmonics for a final definitive synthesis.
• ampfac
Amplitude scale factor for the outfile (multiplier).
Any amplitude transformations applied to the analysis file can be adjusted here either to reduce level (to avoid numeric overflow), or of course to increase itl if necessary. The at command in monan can be used to find out, for example, if the level will be too high (for a 16bit soundfile it must be less than 96dB). A scale factor of 2 increases amplitude by 6dB, and the reciprocal factor of 0.5 (i.e. 1/2) reduces level by the same amount. It is generally good practice to leave a small amount of amplitude headroom  - peak level should therefore be not above 93dB (i.e. -3dB below peak in studio terms).
• dur
set  the duration for the outfile (seconds). See the description of each program for particular restrictions and refinements.

addsyn

Do plain resynthesis of .an format analysis file. There are no modification parameters. Use this to check the quality of the analysis, and to see if the fundamental frequency used for the analysis is appropriate.

Command line:

addsyn [-x][-f][-i] infile outfile
 

addsyn1

Additive synthesis with time-stretching, pitch shifting and amplitude rescaling.  Note that time compression (reducing the duration) is not supported (see addsyn3). Thus the value for dur must be less than that of the analysis file.

Command line:

addsyn1 [-x] [-f] [-i] infile  outfile  sr  f1  nhar  ampfac  dur

(Refer to Common parameters  for descriptions of all parameters.)

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addsyn2

Three-segment time-varying resynthesis with pitch-shfting and amplitude scaling. This allows independent time-warping of the attack, sustain and decay segments of the sound's amplitude envelope. This can be used for arbitrary time-warping effects, or for special modifications of instrument tones with a clear attack-sustain-decay envelope. A typical application in this case is to perform time stretching or compression while preserving the attack and/or  decay. Or, similarly, to modify the attack or decay leaving the rest of the sound unchanged. To find suitable values for the time parameters, examine the overall amplitude envelope (use the at command in monan).

Command line:

addsyn2 [-f][-i][-x] infile  outfile  sr  nhar  ampfac  tfac1  t1  tfac2  t2  tfac3

Special parameters:
 

• tfac1

 
Sets the scale factor for time-warping  the first segment (presumed to embrace the attack stage of the sound). A value of 1 preserves the original duration. Smaller  values compress duration, larger values stretch duration.
• t1
Defines the time marking the end of the first envelope segment, in the analysis file. This segment will be time-stretched or time-compressed according to tfac1.
• tfac2
Sets the scale factor for time-warping  the middle segment (presumed to embrace the sustain stage of the sound). A value of 1 preserves the original duration. Smaller  values compress duration, larger values stretch duration.
• t2
Defines the time marking the end of the sustain segment, in the analysis file (thus, the sustain segment is from t1 to t2). This segment will be time-stretched or time-compressed according to tfac2.
• tfac3
Defines the scale factor for time-warping the last envelope segment in the analysis file (presumed to mark the start of the decay stage of the sound). Thus the decay stage is defined to run from t2 to the end of the file. A value of 1 preserves the original duration. Smaller  values compress duration, larger values stretch duration.

addsyn3

Time-compressed additive synthesis using interpolation, with pitch shifting and amplitude scaling.

This is a special variant of addsyn designed specifically for reduction of duration leaving the attack and decay segments unaffected. Reduction is performed usign a special interpolation method that preserves transient detail.

Command line:

addsyn3 [-f] [-i] [-x]  infile  outfile  sr  f1  nhar  ampfac  t1 t2 dur

 
Special parameters:
 
• t1
time marking the start of the sustain segment to be compressed (end of the attack).
• t2
time marking the end of the sustain segment to be compressed (start of the decay). The length of the decay segment is thus defined as t2 to end_of_the_sound.
• dur
new (shorter) duration for the whole sound. Must be at least the sum of the lengths of the attack and decay segments, i.e. at least t1 + (end_of_the_sound - t2). It must also be less than the current duration of the sound. It follows that if t1 and t2 are close, there is little scope for reduction.

mqsyn2

Additive synthesis of .mq format ( partial-track) analysis files, with acceleration/deceleration and amplitude scaling.

This is the only program available in the  SNDAN suite for direct synthesis from .mq format analysis files. It is provided primarily as a means of checking the quality of the analysis; in most cases you will want to convert the file into .an format, for use with the addsyn programs and monan.

Nevertheless, one transformation unique to this program is the ability to accelerate or decelerate the sound from  start to end, in addition to the ability to apply fixed time-scaling.

Command line:

mqsyn2 [-f] infile  outfile  timefac1 timefac2 [ampfac] [sr]

NB:  in this program, if sr = 0, the internal default sample rate of 22050 is used.

Special parameters:
 

• timefac1
time-scale factor to apply at the start of the sound.
time-scale factor to reach by the end of the sound.

Values are multipliers; a value of 1 signifies no time-scaling.
Values above 1 lengthen the sound progrssively (deceleration), values below 1 shorten the sound (acceleration). Where both values are the same,  the effect will be of a fixed time-scaling.
For example, with timefac1 = 1 and timefac2 = 3, the sound will start at the original speed, and drop to one third of the original at the end. Pitch is unaffected. However, the process cannot be relied upon to be clean in all cases, as new interference patterns not present in the original may be created, leading to unexpected phasing effects.