According to tradition, Brahma Yajna has two parts. One is recitation of Veda. Another is deva- rishi-pitru tarpaNam.
Brahma Yajna has to be performed on a daily basis after mAdhyAnikam. Alternatively, it can be performed in the order : Brahma Yajna (Vedic recitation) --mAdhyanikam -- deva- rishi-pitru tarpaNam. Please note that this is a nitya karma which has to be done daily. According to TaittirIYa AraNyakam, one who daily performs Brahma Yajna reaches the Brahman. BrahmaNas sAyujyam gacchati. Now since most Brahmins have given up this daily practice, it is being done at least on the day of upAkarma.
One important aspect is that this daily Pitru tarpaNam has also to be performed by a person whose father is alive.