Origins
The word 'legato' is a musical term that describes one of the most prized qualities in performance: the ability to make notes flow seamlessly into one another, as if bound together in an unbroken line of sound. It is Italian for 'bound' or 'tied,' and its etymology connects it to one of the most prolific Latin roots in the English language.
Italian 'legato' is the past participle of 'legare' (to bind, to tie), from Latin 'ligāre,' which means the same. The Proto-Indo-European root is *leyǵ- (to bind), which also produced Old English 'līc' (body — something bound together) and possibly 'like' (of similar binding or form).
The English descendants of Latin 'ligāre' form an impressive family. 'Ligament' (a band of tissue that binds bones together at a joint) is the most literal medical descendant. 'Ligature' (a binding, especially a thread used to tie off blood vessels in surgery, or a typographic device joining two letters) is another direct borrowing. 'League' (an alliance — a binding together of parties) came through Old French 'ligue.' 'Ally' (from Old French 'alier,' to bind to) and 'alloy' (from Old French 'aleier,' to combine metals — to bind them together) are the same root with the prefix 'ad-' (to). 'Oblige' (from Latin 'obligāre,' to bind toward, to put under obligation) binds a person to a duty. 'Rely' (from Old French 'relier,' to bind back to, to rally to) expresses trust as a form of binding. 'Religion' — if one accepts Lactantius's etymology from 'religāre' (to re-bind) — describes the binding of humanity to the divine.
Development
In musical practice, legato is achieved by minimizing the silence between notes. On the piano, this means holding each key until the next key is depressed, so that the sound of one note overlaps slightly with the beginning of the next. On string instruments, legato means playing multiple notes in a single bow stroke. On wind instruments, it means tonguing lightly or not at all between notes, maintaining continuous airflow. For singers, legato is the most fundamental technique — the ability to sustain a smooth, unbroken vocal line is the foundation of all beautiful singing.
The notation for legato is a curved line (a slur) connecting two or more notes. Under a slur, the performer is instructed to play the notes as smoothly and connectedly as possible. The contrast between legato and staccato — bound versus detached, connected versus separated — is one of the primary axes of musical expression, and every performer navigates between these poles constantly.
Chopin is often cited as the supreme master of legato writing for the piano. His nocturnes, with their long singing melodic lines over flowing accompaniment, demand a legato technique that makes the piano sing — overcoming the instrument's inherent limitation that, unlike a voice or a violin, its sound begins to decay the moment a key is struck.