A brief overview of the Persian  roba‘i/robaa‘i (رباعی ) meter: (principal source -- Finn Thiesen §255 - §260 ,  Manual of Classical Persian Prosody)

As others have done,Thiesen relates the fanciful story of young boys playing marbles.  It seems that, let's say around 900 C.E., the poet, Rudaki, was close by and heard one of the lads exclaim:

غلتان غلتان همی رود تا بن گو

ghaltaan ghalataan hami ravad taa bon-e gow

"Rolling, rolling, doth it go to the bottom of the hole"

The poet then realized, through familiarity with metrical formulae, that what he heard was similar to the hazaj meter.  And so the robaa‘i meter was said to have evolved from this utterance:   

ghal taan   gha  la   taan    hami  ra vad    taa  bo ne gow

ˉ     ˉ    ˘   ˘   ˉ    ˘  ˉ  ˘  ˉ   ˉ   ˘  ˘   ˉ

Variation from the standard hazaj meter* is astounding; however, Thiesen shows the allowed substitutions.Yet once these substitutions are applied and the meter is arrived at, the actual robaa‘i line isn't so straightforward as the charming example above. Continuing to use the (western) classical long/short style and reading from left to right, we find that 2 shorts = 1 long, even if the shorts do not stand side-by-side, so a line could actually "read" all longs:

     ˉ  ˉ  ˉ ˉ     ˉ ˉ ˉ       ˉ ˉ  ˉ

The "middle section," as I am calling it, shows considerable variation.  It is generally accepted that these 3 patterns are standard for this meter- again reading from left to right: 

                                           ˘ ˉ ˘ ˉ 

                                    ˉ ˉ ˉ

                      ˉ ˘ ˘ ˉ

But these variations can also occur in this section (left to right):

                  ˉ ˘ ˉ ˘

                  ˉ ˉ ˘ ˘

                  ˘ ˘ ˉ ˉ

So, dear visitors, you might not be surprised to hear that this meter at times tends to perplex and frustrate readers!   An important point: the individual lines of a quatrain are not required to conform to the same metrical pattern!  And also, you will see that a line can be scanned two different ways.  A useful tool for khayyaamic metrics can be found in Connie Bobroff's site.  By this selection you will see Quatrain 4 on our site, scanned and recorded for sound.  By choosing "Next Quatrain" above the picture inset, you will find three more quatrains attributed to Khayyaam, audio only (these quatrains correspond to our site's Quatrains 3, 55, and 24 in this order). 

*The hazaj meter:

 ˘ ˉ ˉ ˉ/ ˘ ˉ ˉ ˉ/˘ ˉ ˉ ˉ/˘ ˉ ˉ ˉ 

Now, about rhyme:  If we use as an example, Quatrain 3 in our text (Dashti 9; Forughi-Ghani 34; Hedaayat 10), this robaa‘i below shows the customary layout of the quatrain, "side-by-side". We have abandoned such a format in our weblog quatrains in favor of a line-by-line arrangement.  Observers will see in the quatrain below, the same rhyme scheme (a a b a) as found in the first 4 lines of ghazals  This is the usual pattern; however, the scheme a a a a is also employed in quatrains, as we see in Quatrains 1 and 2 of Exploring Khayyaam. (Throughout the Journal I will also use mesraa‘ instead of "line" and bayt instead of couplet, that is, two lines.  Since Thiesen's text is generally unavailable, those interested might wish to consult Elwell-Sutton's article ‘arûż in the Encyclopaedia Iranica, especially the first 3 paragraphs of his essay on metrics.)

Visitors will see that the rhyme in the quatrain below is -aa + shod. In Quatrains 1 & 2, the rhymes are -aast (1) and -ast (2).  Often the khayyaamic rhymes extend to several, as many as five, syllables.  

   یک قطرهٔ  آب  بود با دریا شد             ذرهٔ خاک با زمین یکجا شد  

 آمد شدن تو اندرین عالم چیست            آمد مگسی پدید و نا پیدا شد