Drummers such as Kenny Clarke and Max Roach were extending the path set by Jo Jones, adding the ride cymbal to the high hat cymbal as a primary timekeeper and reserving the bass drum for accents. Bass drum accents were colloquially termed "bombs," which referenced events in the world outside of New York as the new music was being developed. The new style of drumming supported and responded to soloists with accents and fills, almost like a shifting call and response. This change increased the importance of the string bass. Now, the bass not only maintained the music's harmonic foundation, but also became responsible for establishing a metronomic rhythmic foundation by playing a "walking" bass line of four quarter notes to the bar. While small swing ensembles commonly functioned without a bassist, the new bop style required a bass in every small ensemble.