This research paper is a critical approach to the external music in Nimayian poetry. We have examined some topics with examples of contemporary poetry, topics such as wrap method, the end of the hemistich, the use of prosodic options, and misleading effect of external music in Nimayian poetry. We also have detected shortcomings at the laws of prosody, done by the scholars, or the implementation of the law, by the poets. We tried to add some provisions and amendments to previous laws, to make it easier for scholars and poets to recognize the intricacies of external music in Nimayian poetry and get the best out of it.  This article has five parts. Here are the contents of each section separately and summarily: 1. Wrap method in Nimayian poetry Most of the great poets, accepted wrap based on prosody`s law, but sometimes the law is in contrast with the meaning of sentences, and poet is forced to move short part of  a sentence in one hemistich to another or A sentence has to be divided into several parts. It is better to match the sentence structure to the structure of prosody. Isolated short parts of a sentence and use of one or two syllables in each hemistich are signs of poet`s weakness in prosody. 2. The end of hemistiches Contrary to popular belief, making hemistiches Short or long is not completely free in Nimayian poetry, because short syllables at the end of hemistiches considered as long syllables and if we end the hemistiches with short syllables the mathematical order in syllables chain will fail.  3. Prosodic options and necessities Use of prosodic options in Nimayian poetry sometimes can be the reason of dissonance in the external music and make it difficult to understand the main meter, because In classic poems equality of hemistiches help us to find the meter, but in Nimayian poetry hemistiches are unequal and sometimes in short hemistiches by utilization of one prosodic option or necessities, the external music seems abnormal.   This section has four parts: 1/3. Prosodic options and necessities in first hemistich of poem  Meter is still not known in first Hemistich of poem, and use of prosodic options and Necessities can make it difficult to understand the true meter, therefore it is better to not using it in this Place.  2/3. Taskin  It is better to not using taskin at the end of hemistich and if you did, you should not repeat it in several line, because if you do, the meter seems different. 3/3. Eshba' in one-syllabic words It is better to not using eshba' in one-syllabic words, because it is not appealing in the musical aesthetics. 4/3. Several prosodic options and necessities in one hemistich According to the musical aesthetics using several prosodic options and necessities in one hemistich of poem is not pleasant.  4. Unexpandability of external music in some meters Meters with united prosodic elements are easily comprehensible and in each of the long syllables, the hemistich can be finished, but in meters with intermittent prosodic elements which are made of two different prosodic elements, the elimination of one element and finishing hemistiches is impermissible. 5. Misleading effect of external music Long and short of hemistiches in some meters is misleading, specifically in this syllables chain: «- -  U - U -  U U - - U - U - ...» In classic poems, long and short of hemistiches are not permitted and we can recognize prosodic false by counting syllables, but in Nimayian poetry hemistiches are unequal and sometimes detecting prosodic false is difficult and for this reason, even great poets in Nimayian poetry made mistakes in prosody. We have given some examples in this regard.