Mendes often changed the lineup. Vocalist Sylvia Dulce Kleiner (Bibi Vogel) (1942 - 2004) was replaced by Janis Hansen, who in turn was replaced by Karen Philipp. Veteran drummer Dom Um Romão teamed with Rubens Bassini to assume percussionist duties. Claudio Slon joined the group as drummer in 1969, and went on to play with Mendes for nearly a decade. Sebastião Neto took over on bass and Oscar Castro-Neves took on guitar. These changes gave the group a more orchestral sound than before. In the early 1970s, lead singer Hall pursued a solo career and became Alpert's second wife. Some accounts claim that Mendes was upset with Alpert for years for "stealing" Hall away from his group.