Alternate tunings other than symmetrically stepped-down versions of standard or drop-D tuning (where the lowest string is tuned down two half-steps for simple barred power or fifth chords) are rare in modern classical guitar music, but before the nineteenth century they occurred more often. Drop-D tuning remains common. The sixteenth-century guitar typically had four courses (rather than six strings, as the modern classical does), and the seventeenth-century and eighteenth-century guitar typically had five courses. These were subject to a variety of tunings, such that there is some difficulty establishing which, if any, to consider the standard tuning from which the others deviate. It is sometimes suggested that classical guitarists wishing to read Renaissance lute or vihuela tablature tune their guitar E-A-d-f-b-e' since these instruments in this period usually have the major third between the 3rd and 4th strings.