4.4 Barry
Truax
Barry Truax
has written a number of granular synthesis pieces such as
Riverrun,
The
Wings of Nike, and Tongues of Angels. (Truax 1990: 120)
Riverrun
is Truax's first venture into granular synthesis, and is another landmark
piece in granular synthesis. This is the first composition to rely fully
on real-time granular synthesis techniques. Xenakis started off with an
integration of instruments and granular synthesis. Roads used an integration
of granular synthesis with a number of other computer music methods, which
were impossible to create in any real-time environment. It took more than
enough processing time without having to replay instantaneously as it was.
(Truax
1988b)
Barry Truax
described Riverrun as representing the flow of a river. As with
water, each countless grain of sound flows away, yet the river itself remains
as it was. (Truax 1988b) Like a drop of water each grain on its own is
trivial and powerless, but when it accumulates it becomes like a strong
flowing wave of immense power.
Riverrun
was entirely written using real-time granular synthesis techniques mixed
onto 32 tracks. It consists of grain densities between 1 and 2375. All
of the grains used in this piece were created using either the basic sine
wave method or by using FM Synthesis as the grain content. (Truax 1990:
120) The envelopes used by Truax were limited to linear envelopes. He used
Triangular and Trapezium shaped envelopes. They were all linear because
it allows for much faster processing, which is crucial in any real-time
environment. (Truax 1988: 14)
In
Riverrun
each grain has been defined with an individual frequency and duration.
Truax said "When the grains all have similar parameters, the result is
a pitched and amplitude modulated sound,but when random variation is allowed
in a parameter, a broad-band noise component is introduced." (Truax 1988b)
Looking
at the spectrum of this piece there is a lot to see. There are some very
distinct streams that are going on in the piece. See figure 4.4.
| Frequency
|
 |
| Time |
Fig 4.4: Spectral analysis of Riverrun. Created with Cooledit96 (Shareware).
This piece
ranges from 20Hz to 22KHz. It is on a linear scale. The duration is
just under 20 minutes.
It looks
as if the song was built by putting large chunks of ideas together. It
was created using tendency masks to control all of the parameters, which
may account for the blocked appearance. Despite the look the texture is
very continuous. There is always something flowing through between the
different ideas. The sections in the high frequency range look like they
fluctuate a lot, but this is not actually the case. This is because at
such high frequencies the sense of pitch doesn't change very much at all,
therefore a large movement in a high frequency may only sound like it is
moving a couple of tones. The entire piece spans 20 minutes.
This piece
starts off very calm with occasional bubbly noises. The bubbly noises are
created by long duration grains with a very low grain density 1-20 grains
per second. These grains can be seen on the three dimensional chart (appendix
3:1). Slowly the bubbles become more frequent, resulting in a gradual
accumulation of sound. The sound becomes very intense as the texture builds
up in density. As the density increases the duration of the grains is reduced
(see Appendix 3:2). Then a much higher pitched
group of grains move across the top of the piece, moving a little but not
changing a lot (see Appendix 3:3). They
fade out and the lower granular noise also fades leaving a clapping noise
very similar to horse hooves (see Appendix 3:4).
This clapping type noise must have been made using extremely short duration
grains with a very broad spectrum at a very high density. It is interesting
to note that Truax slowly increases the duration of the grains within the
clapping sound, so that they lose their spectrum and with it their ambiguous
pitch. This gives us a better look inside the sound. We can see that it
is made by having a large spread of grains across the frequency, but with
a very short duration this spread gets lost and the entire bandwidth gets
filled. Truax has made sure the lower frequencies of the spectrum are especially
dense to give it the extra thudding sound.
The next
section of the piece goes into more randomly generated clouds of sound
(see Appendix 3:5). This sounds more like
a chattering type of sound, not dissimilar to Paul Lansky's piece Idle
chatter, except that Truax generated this using sine waves, rather
than sampled vowel sounds. It sounds like thousands of tiny voices all
trying to talk or shout at once. They are obviously randomly pitched because
the texture slowly evolves to a single pitch. It then boils to a very hollow
type of bubble texture, within multiple frequencies. It is as if there
is a definite sense of pitch within the bubbles, but then they go very
quiet. This may be derived through using pairs of triangular envelopes
over waves, so that it appears to give an attack and then release with
nothing in the middle, whereas it is two separate grains.
The piece
seems to concentrate more in pitch areas from this point on. For a while
it sounds like Truax has created a very deep cello, lower than ever possible
for an acoustic instrument. The low sound moves slowly up and down in pitch
(see Appendix 3:6). The last idea in the
texture is a sustained sound that changes in timbre, and moving harmonics.
In summary,
Truax explores a number of different textures, and the ways that can be
moved between them. His main method of changing the texture is to bring
in random pitches that are either very bubbly, or hollow types of sounds.
The sounds he explores are very varied, from imitating claps to changing
timbres and frequencies.