A bit low on my tragically penetrating commentary, but the knowledge is exactly worth itself:
Los Jaivas, "La Poderosa Muerte" [live 1978], originally from Alturas de Machu Picchu (1978)
Incredible stuff from perhaps my favorite '70s disco suramericano: Los Jaivas combined the vanguard of European prog, shorn of any of the aesthetic obesities into which it was deteriorating during the era (I will ride hard for Yes until 1974; for Tormato, I shall ride hardly at all) and coated with an impressively prescient pre-postpunk/new wave ominousness and eerie foreboding perhaps best compared to their Belgian counterparts Univers Zéro or the more determinedly dark moments in Henry Cow's catalog ("Nine Funerals of the Citizen King," for example), and combined these with the fecund ghosts of Andean folk music, with those tenebrous and rarefied Peruvian tones before the era of "world music" blandness and reification. This is music of interstices, of spacio-temporal intersections, of the areas-in-between standing a parallel hemisphere away from those J.G. Ballard was exploring at the same moment. The whole album is crucial, but "La Poderosa Muerte" might be its best track ... there is a startling difference in immediacy and air texture between the doomsayings of a Europe in post-decadent decline and a Peru that has weathered innumerable massacres and knows well enough to expect more of the same. (And let's be frank: the shots of Eduardo Parra wrestling his Mini-Moog and Rhodes on the steps of a decaying Machu Picchu rampart and of Eduardo "Gato" Alquinta--whose 2003 funeral lasted three days and drew 250,000 Chileans--killing the guitar solo from a mountaintop are straight ill.)
Los Jaivas, "Aguila Sideral," Alturas de Machu Picchu(1978)
The composition that made me a fan and opened up South American rock in general to me ... really rather terrifying.
Almendra, "Muchacha (Ojos de Papel)," Almendra (1969)
A lovely folk-pop song, with proleptic echoes of the first couple of Big Star LPs in the vocal delivery and backing harmonies, from one of the two Romulus-and-Remus originary bands in the Argentinian experimental/progressive rock scene of the '60s and '70s; Luis Alberto Spinetta, leader of Almendra and the later Pescado Rabioso, Invisible, and Spinetta Jade, and Charly García, of Sui Generis and Serú Gerán, are generally considered the two most innovative and historically important figures in that lineage.
Anacrusa, "Calfucurá" [live] (1987)
Probably my favorite of the Argentine '70s experimental rock groups, Anacrusa managed to forge a really exceptionally well-balanced alchemy of Piazzolla-style tango influences, diagonally-inclined gridworks of electric guitars, bits of jazz improvisation, and a rhythm section that bore the fluid energy of folkloric pre-Spanish South American dance and ritual rhythms. 1978's El Sacrificio is the only one of their records I know at all well, but certainly one to pick up: the combination of a funereal, almost flamenco saeta-style string arrangement and Susana Lago's very nearly Arabic vocal ululations (highlighting the historical commonalities of the Muslims of southern Spain and their Middle Eastern counterparts, and thus the diaspora of the former among the South American colonies and the natural parallel the peoples of those colonies, indigenous and otherwise, present to their still put-upon Arabic brethren) on the title track is brilliant.
Terreno Baldio, "Grite," Terreno Baldio (1975)
A skewed, jigsawed bit of clockwork reconstructed-medievalism from these Brazilians, often typecast within the tiny segment of the music world that knows their work as "the South American Gentle Giant"--not a bad comparison but by no means an exhaustive one, as there is a desperation and a mannered, baroque darkness (I think of some of the "conspiracy music" from Mozart's operas, for example, or a less drama-school Van der Graaf Generator in rock'n'roll terms) to their work that GG rarely utilized.
Crucis, "No Me Separen de Mi," Los Delirios de Mariscal (1977)
To provide whatchyrcall a unifying thread, Gentle Giant and Argentina tied together like whut--the first couple minutes of this recall In a Glass House or Free Hand for me much more than anything by Terreno Baldio. The low-intensity moderation of the vocal and upending of the usual lead-background dichotomy brings to mind some of Kerry Minnear's more whispery moments for GG, and the delicately funky interlocking Rhodes and guitar at the outset are pure Minnear/Gary Green action, though there's a bit of "Hey Jude" residue in the poppy hook, and the recurring synth/guitar gallop is perhaps more reminiscent of Yes c. Close to the Edge than anything else. Good stuff, though I remain unconvinced that they deserve their status as the most important Argentinian prog group.