How does 'mass participation' relate to the effective mass of
a particular modal shape? Are they analogous?

I've noticed that if the modal is unrestrained, the rigid body modes will account for almost all of the mass participation, and the total in each direction sums to nearly 1, but when the model is restrained the sums become much less. I figure this is because the entire body moves when unrestrained, and so this will account for a large percentage of mass participation, and therefore make other modes seem negligible. Am I right to assume that if I were to compute many more modal shapes (100s, say) for the restrained model that the sum of the mass participation in each direction would indeed add up to 1 (or close to it)?

I've noticed that if the modal is unrestrained, the rigid body modes will account for almost all of the mass participation, and the total in each direction sums to nearly 1, but when the model is restrained the sums become much less. I figure this is because the entire body moves when unrestrained, and so this will account for a large percentage of mass participation, and therefore make other modes seem negligible. Am I right to assume that if I were to compute many more modal shapes (100s, say) for the restrained model that the sum of the mass participation in each direction would indeed add up to 1 (or close to it)?