Roman comedy is mainly represented by two playwrights, Plautus (writing between c.205 and 184 BC) and Terence (writing c.166-160 BC). The works of other Latin playwrights such as Livius Andronicus, Naevius, Ennius, and Caecilius Statius are now lost except for a few lines quoted in other authors. 20 plays of Plautus survive complete, and 6 of Terence.

Various metres are used in the plays. The most common are iambic senarii and trochaic septenarii. As far as is known, iambic senarii were spoken without music; trochaic septenarii (and also iambic septenarii and trochaic and iambic octonarii)Fortson (2008), p. 22. were chanted or recited (or possibly sung) to the sound of a pair of pipes known as (the equivalent of the Greek aulos), played by a ("piper"); and other metres were sung, possibly in an operatic style, to the same .

In Plautus about 37% of lines are unaccompanied iambic senarii,A.S. Gratwick (1982), in The Cambridge History of Classical Literature, vol. 2 part 1, pages 85-86. but in Terence more than half of the verses are senarii. Plautus's plays therefore had a greater amount of musical accompaniment than Terence's. Another difference between the playwrights was that polymetric songs (using metres other than iambic and trochaic) are frequent in Plautus (about 14% of the plays), but hardly used at all by Terence.

The different metres lend themselves to different moods: calm, energetic, comic, mocking, high-flown, grandiose, humorous, and so on. Certain metres are also associated with different kinds of characters; for example, old men frequently use iambic senarii, while the iambic septenarii are often used in scenes when a courtesan is on the stage.

The metres of Roman comedy tend to be more irregular than those of the classical period, but there is an opportunity to hear in them the rhythms of normal Latin speech. Cicero wrote of the senarius: "But the senarii of comic poets, because of their similarity to ordinary speech, are often so degraded that sometimes it's almost impossible to discern metre and verse in them."Cicero, Or. 184: .

The commonest metres A publicly available database by Timothy J. Moore at the Washington University in St. Louis (see External links below) identifies the metre of every line of the two poets (based on the work of Cesare Questa and Wallace Lindsay) and gives detailed statistics for the use of the various metres. From this database it is apparent that by far the commonest metres, accounting for 79% of the lines in the two playwrights, are the following two: Iambic senarius (ia6): 11,170 lines | x – x – | x, – x – | x – u – | Trochaic septenarius (tr7): 10,019 lines | – x – x | – x – x || – x – x | – u – |

In the above schemata, the symbol "–" represents a long element or , "u" a short element or , and "x" an , an element that can be either long or short. The schemata in this section are the basic patterns, and do not take into account the variations which may occur, for example the substitution of two short syllables for a long one. These are explained in greater detail below.

The following iambic and trochaic metres are also found but are less common: Iambic septenarius (ia7): 1,718 lines | x – x – | x – u – || x – x – | x – – | Iambic octonarius (ia8): 1,267 lines | x – x – | x – u – || x – x – | x – u – | (type A) | x – x – | x – x – | x, – x – | x – u – | (type B) Trochaic octonarius (tr8): 211 lines | – x – x | – x – x || – x – x | – x – – |

The following metres are used for songs, and are found mainly in Plautus: Bacchiac quaternarius (ba4): 375 lines | x – – | x – – || x – – | x – – | Cretic quaternarius (cr4): 259 lines | – x – | – u – || – x – | – u – |

The following anapaestic metres are found only in Plautus but not in Terence: Anapaestic septenarius (an7): 216 lines | uu – uu – | uu – uu – || uu – uu – | uu – – | Anapaestic octonarius (an8): 212 lines | uu – uu – | uu – uu – || uu – uu – | uu – uu – | Anapaestic quaternarius (an4): (at least) 135 lines | uu – uu – | uu – uu – |

Together, the ten metres listed above account for all but about 1% of the 27,228 lines of the two poets.

Differences between Plautus and Terence

The metres are used in different proportions by the two playwrights. In Plautus, 47% of the lines are iambic, 43% trochaic, and 10% in other metres (mostly anapaestic, bacchiac, and cretic). In Terence, 75% of the lines are iambic, 24% trochaic, and only 1% in other metres (bacchiac and cretic).

In Plautus, 37% of the lines are unaccompanied iambic senarii, but in Terence 56%. More than 4% of Plautus's lines are anapaestic, but this metre is not used at all in Terence. The trochaic septenarius is much more frequent in Plautus (41%) than in Terence (22%). The trochaic octonarius is slightly more frequent in Terence (1.5%) than in Plautus (0.6%). On the other hand, Terence makes much more use of the iambic octonarius metre than Plautus.

In Plautus a change of metre often accompanies the exit or entrance of a character, and thus frames a scene.Moore in Terentius Poeta, p. 95.Fontaine & Scafuro, p. 491. At other times it indicates a change of pace, such as when Amphitruo's slave Sosia changes from iambic octonarii to a cretic metre when he begins to describe a battle.Amphitruo 219ff.

In Terence different metres accompany different characters: for example, in each of Terence's plays, the woman loved by a young man uses iambic septenarii; in the Heauton Timorumenos, Eunuchus, and Phormio, one of the two young men is associated with trochaics, the other with iambics.Moore in Terentius Poeta, p. 96. Thus there can be frequent changes of metre within a single scene.

About 15% of Plautus's plays on average consists of polymetric cantica (songs in a mixture of metres).Fontaine & Scafuro, p. 487-8. In these, the most common metres are the bacchius (x – – ) and cretic (– x –), together with anapaests (u u –), but sometimes with other metres mixed in. One play (Miles) has no polymetric cantica, but Casina has four. Because of metrical ambiguities, the analysis of the metres of cantica can be disputed.

The ABC metrical pattern It has been noted that in both playwrights, but especially in Plautus, the use of different metres tends to form a pattern, which Moore refers to as the "ABC succession".Moore, Music, pp. 237-42, 253-8, 305-8, 367-71. Often a play can be divided into sections, which follow the pattern: A = iambic senarii, B = other metres, C = trochaic septenarii. In Plautus's Menaechmi, for example, the first four sections follow the ABC scheme, and only the 5th is different; thus the whole scheme is ABC, ABC, ABC, ABC, ACBCBC. In his Pseudolus, in the same way, the ABC pattern is used four times, followed by a final scene of 91 lines in other metres, making ABC, ABC, ABC, ABC, B. However, not all plays follow this scheme. For example, in Terence's Adelphoe, the pattern is ABCBAB, ABC, BCACB, AC, ABABC. In general it appears that Terence changes mode more frequently than Plautus.Moore, Music, p. 255. Four of Plautus's plays (Cistellaria, Stichus, Epidicus, and Persa) open directly with music, omitting the customary expository speech in unaccompanied iambic senarii.Moore, Music, pp. 243-5.

The B-sections of the plays tend to be songs in which the characters express their mood or character, or sing of love. The C-sections (in trochaic septenarii) tend to be associated with advancement of the plot. "The beginning of the first long series of trochaic septenarii usually marks a moment at which, after exposition and presentation of character, the plot begins to proceed in earnest." (Moore)Moore, Music, p. 249. When a playwright moves directly from A to C, it often marks urgency or an especially significant moment in the plot.Moore, Music p. 255.

Verse ictus and word accent Ictus In his , Horace described the senarius as having "six beats" ().Horace, Ars Poētica 253. However, there is some controversy among scholars over what this means and to what extent word accent played a role in Plautus and Terence's verse.Denniston, J.D., Article "Metre, Greek", Oxford Classical Dictionary 2nd ed. p. 680.See also Sturtevant (1929); Beare (1953).

On one side, supporting the idea of an ictus or beat, are scholars such as W. Sidney Allen,Allen, W.S. Vox Graeca, 2nd ed. (1974) p. 120, 3rd ed. (1987) p. 132. Lionel Pearson,Pearson, Lionel (1990). Aristoxenus: Elementa rhythmica. The fragment of Book II and the additional evidence for Aristoxenean rhythmic theory (Oxford), p. xxxiii. and from an earlier generation E.H. Sturtevant and Wallace Lindsay.Lindsay, Captivi, pp. 861ff. Sturtevant writes: "It is scarcely possible any longer to doubt that accent was an important feature of early dramatic verse; the quantitative nature of the measures was carefully preserved, but at the same time accent was constantly taken into account."Sturtevant (1919), p. 244.

However, many scholars, such as Paul Maas, Cesare Questa, and Wolfgang de Melo argue that there was no beat or "ictus"; in their view, rhythm is "simply the regulated sequence of short and long syllables". Similarly, Benjamin Fortson writes: "The theory that there was a verse-ictus, never universally accepted, has by now been thoroughly discredited."Fortson, B. in James Clackson "A Companion to the Latin Language". Wiley-Blackwell (2011); Fortson (2008), pp. 30-33. Gratwick, in his edition of the Menaechmi, takes an intermediate position, rejecting "both the Anglo-German view that the lines are isochronous with a regular metrical beat attached to every longum, and the Franco-Italian view that there is no ictus at all in such verses".Groton (1995).

One fact which is generally agreed on is that in iambic and trochaic metres, there is usually a fairly strong agreement between where the ictus is assumed to be and the accent of the words. Thus in iambics a word-accent is generally heard on the 2nd, 4th, 6th and 8th elements of the line: Plautus Aulularia 1 | – – – – | – – – – | – – u – | "In case anyone is wondering who I am, let me explain briefly."

Whereas in trochaics, the accent is usually heard on the 1st, 3rd, 5th, and 7th elements: Plautus Amphitruo 459. | – – – – | – – – – || – u – uu | – u – | "It's happening to me alive what no one will ever do to me when I am dead!"

Thus even though both lines begin with a series of long syllables, it is clear on reading them that the first is iambic and second trochaic.

The match between accent and ictus is not exact. For example, in the final metron of an iambic line, there is often a clash between ictus and accent. Gratwick's view is that so far from attempting to make the word accent match the ictus, Roman writers often deliberately tried to avoid such coincidence, especially at the beginning and end of the line, to avoid monotony.

The following table shows the percentage of anceps positions in the iambic senarius which are accented. It is based on a survey by J. J. Schlicher of the 533 iambic senarius lines in Plautus's .Schlicher (1902), p. 50. Overall only 20% of anceps positions are accented. The 2nd, 3rd and 4th are rarely accented, but in the 5th and 6th there is quite often a clash of accent and metrical ictus:

anceps 1st 2nd 3rd 4th 5th 6th +accent 26% 8% 7% 12% 32% 44%

There is disagreement, however, about whether this avoidance of accent in the 2nd, 3rd, and 4th anceps was deliberately aimed for by the poets, or whether it just happened automatically as a result of placing a caesura after the 5th element.