Forms of sacred music which developed during the late 13th century included the motet, conductus, discant, and clausulae. One unusual development was the "Geisslerlieder", the music of wandering bands of flagellants during two periods: the middle of the 13th century (until they were suppressed by the Church); and the period during and immediately following the Black Death, around 1350, when their activities were vividly recorded and well-documented with notated music. Their music mixed folk song styles with penitential or apocalyptic texts. The 14th century in European music history is dominated by the style of the "ars nova", which by convention is grouped with the medieval era in music, even though it had much in common with early Renaissance ideals and aesthetics. Much of the surviving music of the time is secular, and tends to use the formes fixes: the ballade, the virelai, the lai, the rondeau, which correspond to poetic forms of the same names. Most pieces in these forms are for one to three voices, likely with instrumental accompaniment: famous composers include Guillaume de Machaut and Francesco Landini.