Portato is a bowing technique for stringed instruments (Anon. 2001), in which successive notes are gently re-articulated while being joined under a single continuing bow stroke. It achieves a kind of pulsation or undulation, rather than separating the notes. It has been notated in various ways. One early 19th-century writer, Pierre Baillot (L’art du violon, Paris, 1834), gives two alternatives: a wavy line, and dots under a slur. Later in the century a third method became common: placing "legato" dashes (tenuto) under a slur (Wall 2001a). The notation with dots under slurs is ambiguous, because it is also used for very different bowings, including staccato and flying spiccato (Walls 2001a; Walls 2001b).
Currently, portato is sometimes indicated in words, by "mezzo-staccato" or "non-legato"; or can be shown by three graphic forms:
a slur that encompasses a phrase of staccato notes (the most common), or
a tenuto above a staccato mark (very often), or
a slur that encompasses a phrase of tenuto notes (less common) (Tsai 2008).
Walls, Peter. 2001a. "Bow, §II, 3. Bowstrokes after c1780, (iii) Portato". The New Grove Dictionary of Music and Musicians, second ion, ed by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.
Walls, Peter. 2001b. "Bow, §II, 3. Bowstrokes after c1780, (vi) Staccato". The New Grove Dictionary of Music and Musicians, second ion, ed by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.