The first additions to this simple ensemble were a pair of horns, occasionally a pair of oboes, and then both horns and oboes together. Over the century, other instruments were added to the classical orchestra: flutes (sometimes replacing the oboes), separate parts for bassoons, clarinets, and trumpets and timpani. Works varied in their scoring concerning which of these additional instruments were to appear. The full-scale classical orchestra, deployed at the end of the century for the largest-scale symphonies, has the standard string ensemble mentioned above, pairs of winds (flutes, oboes, clarinets, bassoons), a pair of horns, and timpani. A keyboard continuo instrument (harpsichord or piano) remained an option.