When we have an abstract or generic noun:
and we're not speaking of an instance of such, as in "the singing lessons she gives on M-W-F afternoons versus those she gives on T-Th", there is no call for a determiner; it is sufficient to identify the noun with a modifier that provides its type or class:
In effect, the modifier is acting as a determiner.
We determine an abstract or generic noun by identifying a type of it. We determine a concrete noun by indicating whether we mean any noun of its type (a dog) or a particular instance (the dog) or one that is near at hand (this dog) or farther away (that dog) or some subset of its class (few dogs).