Shacharit during Musaf

Hi,

One who comes to shul late, when the community is already reciting the musaf amidah, should still pray in the proper order, reciting the shacharit amidah, rather than recite musaf with the community. According to some opinions, doing this fulfills an element of praying "with the community", despite the fact that one is reciting a different amidah.

(Rivivot Ephraim 1:220)

Have a great day,
Mordechai