His singing could be heard in the stairwell, harmonizing a cappella doo-wop standards between laughs with other members of his group, the Schlamtones. It could be heard in his classroom — he regularly opened class with show tunes. It could even be heard in his voice when he answered his office phone at Northern Illinois University College of Law — a playful, lilting declaration: “Schlam here … ” When Lawrence Schlam died last month of complications due to heart disease at age 72, he …