Origins
The word 'allegro' is among the most familiar of the Italian tempo markings that pervade Western classical music. It entered English in the 1680s as both an adjective (describing a passage's tempo) and a noun (a movement or section performed at a brisk pace). The word comes directly from the Italian adjective 'allegro,' meaning 'cheerful,' 'merry,' or 'lively,' which descends from Latin 'alacer' (genitive 'alacris'), meaning 'lively,' 'eager,' or 'brisk.'
The Latin 'alacer' is of uncertain deeper etymology. Some philologists have proposed a connection to PIE *h₂el- (to grow, to nourish), which would link it distantly to Latin 'alere' (to nourish) and 'altus' (high, deep — literally 'grown'). Others consider 'alacer' a word without clear Indo-European cognates outside the Italic branch. What is certain is that it carried a strong connotation of spirited energy — Roman authors used it to describe eager soldiers, lively horses, and enthusiastic crowds.
In Italian, 'allegro' preserved this sense of cheerful liveliness. It appears in literary Italian from the fourteenth century, and its musical application developed in the sixteenth and seventeenth centuries as Italian composers began systematically writing tempo and expression markings into their scores. The earliest musical uses of 'allegro' were understood primarily as indications of character — 'play this in a cheerful, spirited manner' — rather than prescriptions of a specific speed. The distinction matters: a seventeenth-century 'allegro' might have been performed at a tempo that modern musicians would consider only moderato, because the word described the quality of energy, not the metronome marking.
Latin Roots
This shift from mood-word to speed-word occurred gradually through the eighteenth century. As Italian tempo terms spread across European music, performers who did not speak Italian naturally focused on the tempo implications rather than the emotional ones. The process was completed by the invention of Johann Maelzel's metronome in 1815, which allowed composers to specify exact beats per minute. Beethoven was among the first to add metronome markings to his scores, effectively translating Italian mood-words into numerical values. In modern practice, 'allegro' typically indicates a tempo of roughly 120 to 156 BPM, though interpretation varies.
The same Latin root 'alacer' gave English the word 'alacrity' (eager and enthusiastic willingness), borrowed through Middle French 'alacrité' from Latin 'alacritātem.' The semantic parallel is clear: both 'allegro' and 'alacrity' denote a quality of cheerful, brisk energy. The diminutive form 'allegretto' — literally 'a little allegro' — indicates a tempo slightly slower than allegro, typically 100–120 BPM.
In the broader family of Italian tempo markings, 'allegro' occupies the fast end of the spectrum alongside 'vivace' (lively) and 'presto' (very fast), while 'adagio' (slow, at ease) and 'andante' (walking pace) govern the slower end. Each of these words began as an ordinary Italian adjective or adverb and was specialized through musical usage. This Italian vocabulary became universal in Western music not because Italian is inherently better suited to musical description, but because Italian composers and performers dominated European musical life in the seventeenth and eighteenth centuries, and their terminology became the international standard.
Literary History
Outside musical contexts, 'allegro' appears occasionally in English as a literary adjective meaning lively or brisk, though this usage is rare and self-consciously Italianate. The word's primary home in English remains the concert hall, the conservatory, and the printed score, where it continues to direct performers, three centuries after its adoption, to play with the spirited cheerfulness its etymology demands.