Melancholic: From Marcel Proust's "For an Album of Melancholy: New Ballads from Macedonia"

This is less a constraint and more a poetic form, but demonstrates what happens when particular poems are generalized. It consists of six stanzas. The first, second, fourth and fifth stanzas are four lines long. The third and sixth stanzas are six lines long. The syllabic structure of the poem is as follows:

6866
6866
586656
6866
6866
586656

Just as the Villanelle form invokes obsession through repetition, so too does this form:

1R13
2R21
3R1x23
1R13
2R21
3R1y23

The second line in each stanza, R, is a repetition of the same line verbatim. This line consists of an internal repetition of two four-syllable phrases which may be different from each other. All other numbers stand-in for repeated end-words. The lines marked x and y stand in for words which are not repetitions of any other word but are rhymes of one such word. These should always be proper names. There are two rhyming groups: {1, R, x}; {2, 3, y}. 

EG:

Sometimes Wanna Go, Sometimes Wanna Stay

And it could turn to gray
And sometimes go, and sometimes stay
Surfaces turned to gray
Moving across, ergo 

A single drop, solo
And sometimes go, and sometimes stay
A traced path, so low
Turned to a darker gray

Mentioned it, ergo
And sometimes go, and sometimes stay
The sky kept turning gray 
At time pretend Combray 
In rooms left, so low
Located there, ergo
As unset concrete gray 
And sometimes go, and sometimes stay
And looping off to gray 
And framed into "ergo"

Rereading it so low
And sometimes go, and sometimes stay
And riding past, so low
Through density of gray

On this line, ergo
And sometimes go, and sometimes stay
Mixed up into gray 
Left to dry in Oslo
Seaward left, so low
Located there, ergo...