After another 1 person participated, the number of people participating in the choir accounted for the whole class 1/6.

Then, the corresponding score of this person 1 is:1/6-1/7 =1/42.

So there are students in Class 2: 1÷ 1/42=42.

Comprehensive formula:

1÷[ 1/( 1+5)- 1/7]

= 1÷[ 1/6- 1/7]

= 1÷ 1/42

=42 people