Buff-throated Saltators (Saltator maximus) were heard all around Arenal Volcano. This is an example of their song. It was recorded at La Selva (Costa Rica), 11/16/98 (the descending trill is a Streak-header Woodcreeper)
Here is an example of Variable Seedeater (Sporophila americana) mimicry, recorded on the road leading out of Bribri, near Puerto Viejo de Talamanca (Costa Rica), 6/22/99. The mimicry is delivered in the same style as a Lesser Goldfinch's - rapid fire and each separate song very brief. Listen for Olive-backed Euphonia, Hoffman's Woodpecker, and other species' songs in the sample.