Complex sentence: The orchestra on the album is humorously credited as the "Baroque Ensemble of the Merseyside Kammermusickgesellschaft," though it was likely, in reality, an ad hoc group of session musicians.
Split into simpler sentences: The orchestra on the album is credited as the "Baroque Ensemble of the Merseyside Kammermusickgesellschaft". The players were most likely an ad hoc group of session musicians.