Since a chord may be understood as such even when all its notes are not simultaneously audible, there has been some academic discussion regarding the point at which a group of notes may be called a "chord". Jean-Jacques Nattiez (1990, p. 218) explains that, "We can encounter 'pure chords' in a musical work," such as in the "Promenade" of Modest Mussorgsky's "Pictures at an Exhibition" but, "Often, we must go from a textual given to a more "abstract" representation of the chords being used," as in Claude Debussy's "Première arabesque".