Can a Foreign Key be part of a Composite Primary Key for another table?
Yes, of course. It's common for a subset of a primary key to be a foreign key. Any many-to-many table does this for instance. In your case:
CREATE TABLE ConcertDetails ( ConcertDate DATE NOT NULL, ConcertID INT NOT NULL, PRIMARY KEY (ConcertDate, ConcertID), FOREIGN KEY (ConcertID) REFERENCES Concerts(ConcertID));