A course, on a stringed musical instrument, is either one string or two or more adjacent strings that are closely spaced relative to the other strings, and typically played as a single string. The strings in each multiple-string course are typically tuned in unison or an octave. Normally, the term course is used to refer to a single string only on an instrument that also has multi-string courses. For example, a nine-string baroque guitar has five courses: most are two-string courses but sometimes the lowest or the highest consists of a single string.