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binary form. Literally, a form in 2 sections. Simple binary form, as in an 18th-cent. kbd. suite, has no strong contrast of material. The first section opens in the tonic key and then (subject to an exception shortly to be mentioned) modulates, as it ends, into the key of the dominant. The 2nd section then opens in that 2nd key and, before it ends, modulates back to the 1st. There are, then, 2 distinct main cadences, or points of rest, the 1st in the dominant and the 2nd in the tonic. The exception just referred to occurs if the piece is in a minor key, when the 1st section sometimes ends in the relative major. This form is unsuitable for very long pieces, since the variety offered to the listener is almost entirely confined to details of treatment and the element of key, the thematic material employed throughout being the same. Since the deaths of Bach and Handel, this form has been little used. It developed into compound binary form, another name for sonata form.