Let's start with the Portuguese guitar: a marginal instrument rarely used outside of fado. It's something of a cross between a 12-string acoustic and a medieval lute with vaguely arabic tunings. Astrolabio is a collection of solo improvisations on the Portuguese guitar by Victor Herrero with little regard for the instrument's traditions. The improvisations themselves are of a stubborn variety, focusing on a single technique or whittling short phrases into new shapes with each pass. Herrero is patient and not eager to showcase everything he can do in each song. In this context, the Portuguese guitar sounds more alien than even a custom-tuned guitar, it has a thinner, more harp-like quality—never more than on Fulgor, where it sounds like he is using an e-bow and glass slide.