There are few characteristics common to all blues, as the genre takes its shape from the distinctive attributes of each individual performance. Some characteristics, however, were present prior to the creation of the modern blues, and are common to most styles of African American music. The earliest blues-like music was a "functional expression, rendered in a call-and-response style without accompaniment or harmony and unbounded by the formality of any particular musical structure". This pre-blues music was adapted from the field shouts and hollers performed during slave times, expanded into "simple solo songs laden with emotional content".