context: After 1965, differences between the Hot 100 chart and the Easy Listening chart became more pronounced. Better reflecting what middle of the road stations were actually playing, the composition of the chart changed dramatically. As rock music continued to harden, there was much less crossover between the Hot 100 and Easy Listening chart than there had been in the early half of the 1960s. Roger Miller, Barbra Streisand and Bobby Vinton were among the chart's most popular performers.
question: హాట్ 100 మరియు ఈజీ వినికిడి మధ్య క్రాస్ఓవర్ ఎందుకు తగ్గింది?
answers: rock music continued to harden