user11009: Can we use Piti as a meditation subject?
There are 40 meditation objects are given in Visuddhimagga as follows.
Ten recollections; ten foul objects; ten kasinas; four sublime abidings; four formless absorptions; one resolution into elements; and one perception of the filthiness of food.
My question is whether we can keep four form absorptions as a meditation objects, but specifically Piti as a meditation object.

user8157: Similar to dishonesty about attaining jhana, clinging to rapture & jhana leads to rebirth in hell. Therefore, the Lord Buddha did not teach those who have unshakeable permanent faith in Him to "keep rapture" as meditation object. Instead, the Buddha taught those with unshakeable permanent faith to view impermanent alien diseased rapture with Right View. 

There is the case where an individual, withdrawn from sensuality,
  withdrawn from unskillful qualities, enters & remains in the first
  jhana: rapture & pleasure born from withdrawal, accompanied by
  directed thought & evaluation. He savors that, longs for that, finds
  satisfaction through that. Staying there — fixed on that, dwelling
  there often, not falling away from that — then when he dies he... goes
  to hell
AN 4.123

There is the case where a monk, secluded from sensuality, secluded
  from unskillful qualities, enters & remains in the first jhana:
  rapture & pleasure born of seclusion, accompanied by directed thought
  & evaluation. He regards whatever phenomena there that are connected
  with form, feeling, perception, fabrications & consciousness, as
  inconstant, stressful, a disease, a cancer, an arrow, painful, an
  affliction, alien, a disintegration, an emptiness, not-self. He turns
  his mind away from those phenomena, and having done so, inclines his
  mind to the property of deathlessness: 'This is peace, this is
  exquisite — the resolution of all fabrications; the relinquishment of
  all acquisitions; the ending of craving; dispassion; cessation;
  Unbinding.'
AN 9.36



user295: Piti can be used as a meditation subject.
When one is moving from the 2nd Jhana to the 3rd one notes the Piti and gradually suppress it. In this instance, ones focus it the Piti.

user17168: Anything can be used as an object of meditation.  Hell, you could use a chocolate cake if it tickled your fancy.  But just because you can use anything, it doesn't mean that you should.  The best objects are those that are consistent, stable, repeatedly accessible, and don't give rise to additional mental formations.  The breath is most often used because it checks all of those boxes quite easily.  Piti can meet those same requirements, but until you hit the 1st jhana, it is entirely too unstable and inconsistent.  It can also give rise to clinging and attachment which would ultimately prevent you from moving past the 2nd jhana.  

11009: <p>Can we use Piti as a meditation subject?
There are 40 meditation objects are given in Visuddhimagga as follows.
Ten recollections; ten foul objects; ten kasinas; four sublime abidings; four formless absorptions; one resolution into elements; and one perception of the filthiness of food.
My question is whether we can keep four form absorptions as a meditation objects, but specifically Piti as a meditation object.</p>
 8157: <p>Similar to dishonesty about attaining jhana, clinging to rapture &amp; jhana leads to rebirth in hell. Therefore, the Lord Buddha did not teach those who have unshakeable permanent faith in Him to "keep rapture" as meditation object. Instead, the Buddha taught those with unshakeable permanent faith to view impermanent alien diseased rapture with Right View. </p>

<blockquote>
  <p>There is the case where an individual, withdrawn from sensuality,
  withdrawn from unskillful qualities, enters &amp; remains in the first
  jhana: rapture &amp; pleasure born from withdrawal, accompanied by
  directed thought &amp; evaluation. He savors that, longs for that, finds
  satisfaction through that. Staying there — fixed on that, dwelling
  there often, not falling away from that — then when he dies he... goes
  to hell</p>
  
  <p>AN 4.123</p>
  
  <hr>
  
  <p>There is the case where a monk, secluded from sensuality, secluded
  from unskillful qualities, enters &amp; remains in the first jhana:
  rapture &amp; pleasure born of seclusion, accompanied by directed thought
  &amp; evaluation. He regards whatever phenomena there that are connected
  with form, feeling, perception, fabrications &amp; consciousness, as
  inconstant, stressful, a disease, a cancer, an arrow, painful, an
  affliction, alien, a disintegration, an emptiness, not-self. He turns
  his mind away from those phenomena, and having done so, inclines his
  mind to the property of deathlessness: 'This is peace, this is
  exquisite — the resolution of all fabrications; the relinquishment of
  all acquisitions; the ending of craving; dispassion; cessation;
  Unbinding.'</p>
  
  <p>AN 9.36</p>
</blockquote>

<p><a href="https://i.stack.imgur.com/bpj0y.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/bpj0y.jpg" alt="enter image description here"></a></p>
 295: <p>Piti can be used as a meditation subject.</p>

<p>When one is moving from the 2nd Jhana to the 3rd one notes the Piti and gradually suppress it. In this instance, ones focus it the Piti.</p>
 17168: <p>Anything can be used as an object of meditation.  Hell, you could use a chocolate cake if it tickled your fancy.  But just because you can use anything, it doesn't mean that you should.  The best objects are those that are consistent, stable, repeatedly accessible, and don't give rise to additional mental formations.  The breath is most often used because it checks all of those boxes quite easily.  Piti <em>can</em> meet those same requirements, but until you hit the 1st jhana, it is entirely too unstable and inconsistent.  It can also give rise to clinging and attachment which would ultimately prevent you from moving past the 2nd jhana.  </p>
