Cães Celestes
The second movement, Cães Celestes (Celestial Dogs), is so titled because most of this movement is accompanied by the constellations of Canis Minor and Canis Major. The themes are the gold color and the motto, Ordem e Progresso. Gold is figuratively sonified through the use of pure sine waves, which provided a sonic shimmering, sparkling effect similar to those produced by small tinkling bells. Interestingly, ancient Amerindian picture manuscripts show that symbols of small bells were often used to iconify gold and divinity (Díaz 2007).
The motto is expressed through the use of harmonic progression that sequences these sounds as unordered arpeggios, through a recognizable structure that suggests order and progress. This movement is inspired by the piece New York Skyline for piano by the Brazilian composer Heitor Villa-Lobos. Similar to the way Villa-Lobos maps the pitch of each note the height of the buildings in New York, the pitch of each oscillator is mapped to the altitude of the stars within the field of view in the planetarium display. While Villa-Lobos used the temporal aspect, in the timing of the notes, to indicate their position from left to right in the soundscape, I applied a spatialization technique, mapping the notes to the angle of the celestial azimuth. Additionally, the azimuth was also sonified spatially in that its numerical value determined how far to the left or right the sound was panned.
Mapping the Celestial Dogs
Although right ascension (RA) and declination (Dec.) could be mapped to pitch and time (Fraietta 2014), this does not necessarily correlate to the order of the stars from left to right or top to bottom. Consider the two simulations of the constellation Canis Major at approximately six months apart shown below.
On the image in November, the star Mizram is lower and well to the left of Sirius; however, in May, Mizram is higher and only slightly to the left. The astronomical data for the stars, obtained through VizieR, is identical for both images due to the query input requirements of VizieR. In order to map the vertical and horizontal visual positions of the stars, a conversion from the celestial to the horizontal coordinate system is required for each star in the table. This conversion must be calculated using the geographical location of the observer a GMT, which in this case, was Rio de Janeiro at 8:30 a.m. (GMT-3) on 15 November, 1889. This conversion is known as converting an object’s position in the sky from RA/Dec. to AltAz (Duffett-Smith and Zwart 2011).
As the planetarium software display moves from one star to another, the celestial position of the center of the display, coupled with the field of view—i.e. the amount of sky that is being viewed—are used as input parameters for the VizieR query, which returns a table of astronomic values for all the stars recorded in the Hipparcos catalogue (Van Leeuwen 2007) within that window. This data is sorted by magnitude, with the brightest sixty-four stars selected. The RA/Dec. coordinates of these stars are converted to AltAz values, which are then mapped to pitch and time. Rather than performing a pragmatic conversion using strict audification or PMSon, the data was treated as “raw material, a generated virtual stone [... and sculpted] into musical existence” (Xenakis, cited in Gresham-Lancaster 2012: 208). Rather than playing a series of notes that progressed from left to right, which would result in a horizontal sweep, the sixty-four notes were grouped into sixteen groups of four, with each group played synchronously, effectively creating sixteen four-note chords played sequentially. Similarly, the calculated altitudes are quantized to the nearest note in the defined harmony each time a chord change is made in the movement. Each movement from one star to another is a sequence of ordered changes, shown below.
The movement commences with equally-distributed random frequencies, played concurrently with an image of daylight facing the sun, sonically symbolizing background cosmic radiation. As soon as the visualization of the terrestrial atmosphere is removed, the stars become visible, and the initial progression towards order is sonified through the creation and synchronisation of sound envelopes. The movement to Procyon, in Canis Minor, triggered the loading of a table of notes in which altitude values are quantized into pitches derived from a whole-tone scale. The frequencies are quantized into notes from a natural minor scale during the progression into Canis Major, followed by a shift to its tonic major. A similar tonic minor to major progression occurs when moving to Mirzam.
The movement from Sirius through to Wezen is a ii-V-I turnaround, followed by a major thirteenth coloration change in the approach to Adhara. Advancing to the constellation of Carina generates a temporary discord, effected through the use of chromatic notes. Consonance is restored by means of a major ninth chord when moving to Canopus, the final star. The movement concludes with a migration to the spatial center of all three constellations, coupled with a ii-V-I cadence that disappears with a diminuendo al niente.
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