A due

What it means

A due, abbreviated a2, means “together, in twos” and appears in orchestral parts in which two like instruments are notated on one staff. The marking says that both are to play the same line.

Its counterparts are the markings 1. and 2., with which only the first or the second instrument plays respectively, as well as the notation of two separate voices on the same staff, recognisable by stems pointing in opposite directions. a2 cancels such a division again.

Note a second use: in older music a due also indicates the number of voices in a piece, for instance in a two-part invention or a trio whose title names the scoring. Which meaning applies follows from where the marking stands.

In the notation

The abbreviation a2 stands above the staff at the point from which both instruments play in unison, and holds until a new marking. Where the parts are divided, the figures 1. and 2. appear instead above the respective passages. In string parts the division is indicated with divisi and cancelled with unisono.

Musical use

In the wind section of the orchestra it is usual for two like instruments to share one staff, for example two flutes or two oboes. The alternation between divided and joint playing is a means of sound design: a2 gives the line double weight, division allows two-part writing. In scores the marking shows at a glance how dense the texture is at that point.

In orchestral scores two like winds often stand on one staff. The marking a 2 then cancels the separate running of the two voices and calls for unison; with 1. or I. the writing is reduced to one player again.

Performance practice

When reading your part, check carefully whether a2, 1. or 2. applies — this is easily missed at line breaks. Coordinate articulation and phrasing with your desk partner so that the shared line sounds uniform. Watch the intonation, which stands out at once with two like instruments. And note the places where the marking changes.