I don't know Spanish, but I was familiar with the word through the writing of Federico Garcia Lorca and Pablo Neruda. Here's some excerpts from the Wikipedia entry on "duende":
"El duende is the spirit of evocation. It comes from inside as a physical/emotional response to music. It is what gives you chills, makes you smile or cry as a bodily reaction to an artistic performance that is particularly expressive. Folk music in general, especially flamenco, tends to embody an authenticity that comes from a people whose culture is enriched by diaspora and hardship; vox populi, the human condition of joys and sorrows. Drawing on popular usage and Spanish folklore, Federico Garcia Lorca first developed the aesthetics of Duende in a lecture he gave in Buenos Aires in 1933, "Juego y teoria del duende" ("Play and Theory of the Duende").
"According to Christopher Maurer, editor of 'In Search of Duende,' at least four elements can be isolated in Lorca's vision of duende: irrationality, earthiness, a heightened awareness of death, and a dash of the diabolical. The duende is a demonic earth spirit who helps the artist see the limitations of intelligence, reminding him that "ants could eat him or that a great arsenic lobster could fall suddenly on his head"; who brings the artist face-to-face with death, and who helps him create and communicate memorable, spine-chilling art. The duende is seen, in Lorca's lecture, as an alternative to style, to mere virtuosity, to God-given grace and charm (what Spaniards call "angel"), and to the classical, artistic norms dictated by the muse. Not that the artist simply surrenders to the duende; he or she has to battle it skillfully, "on the rim of the well", in "hand-to-hand combat". To a higher degree than the muse or the angel, the duende seizes not only the performer but also the audience, creating conditions where art can be understood spontaneously with little, if any, conscious effort. It is, in Lorca's words, "a sort of corkscrew that can get art into the sensibility of an audience... the very dearest thing that life can offer the intellectual." The critic Brook Zern has written, of a performance of someone with duende, "it dilates the mind's eye, so that the intensity becomes almost unendurable... There is a quality of first-timeness, of reality so heightened and exaggerated that it becomes unreal..."
"Lorca writes: "The duende, then, is a power, not a work. It is a struggle, not a thought. I have heard an old maestro of the guitar say, 'The duende is not in the throat; the duende climbs up inside you, from the soles of the feet.' Meaning this: it is not a question of ability, but of true, living style, of blood, of the most ancient culture, of spontaneous creation.". He suggests, "everything that has black sounds in it, has duende. [i.e. emotional 'darkness'] [...] This 'mysterious power which everyone senses and no philosopher explains' is, in sum, the spirit of the earth, the same duende that scorched the heart of Nietzsche, who searched in vain for its external forms on the Rialto Bridge and in the music of Bizet, without knowing that the duende he was pursuing had leaped straight from the Greek mysteries to the dancers of Cadiz or the beheaded, Dionysian scream of Silverio's siguiriya." [...] "The duende's arrival always means a radical change in forms. It brings to old planes unknown feelings of freshness, with the quality of something newly created, like a miracle, and it produces an almost religious enthusiasm." [...] "All arts are capable of duende, but where it finds greatest range, naturally, is in music, dance, and spoken poetry, for these arts require a living body to interpret them, being forms that are born, die, and open their contours against an exact present."
What musicians, dancers, and poets have duende in your experience?