A keyboard unit (10) comprising a plurality of keys (12) surrounding a centre (14) and operable singly and chordally by a single finger (or thumb). Preferred arrangements consist of three, four or seven surrounding keys (12), particularly for playing musical notes of an octave. A keyboard (16) may comprise a plurality of spaced apart units (10) in groups (18) operable by respective fingers. The different units (10) may operate different instrumental sounds. Variations include shift functions, operation of lights, e.g. in mixed sequence with notes, operation of alphanumeric characters, e.g. to produce up to a 10-character word or grouping simultaneously. The keyboard (16) may be on the back of a guitar neck (30) or arranged to correspond to the keys on a piano. Logical circuitry and mosaic and adapted QWERTY keyboards are described, also a piano keyboard with phantom black notes.