Solo piano concerts have come to hold a dual, contradictory status. They are ubiquitous in classical circles, where they serve didactic and diagnostic purposes through competitions and senior recitals. They’re also something of an anachronism in the contemporary sonic landscape, where digital listening threatens its live counterpart. Last Wednesday night, pianist Sara Davis Buechner brought something essential back to the Barnes Hall stage that too often eludes the musically inclined among us: humility. It was evident in her curatorial preambles, in which she waxed to the audience anecdotally, passionately and honestly about the history of each piece before playing it.