Not sure if Dhaarna existed in the pre-Sant Attar Singh period but Dhaarna were popularized by Sant Attar Singh jee as a way to do Parchaar of Sikhi. The uneducated rural people, particularly of Malwa region, were very receptive of this style and many took Amrit. Later on many prominent Sants e.g. Sant Rarewale, used the Dhaarna style of singing to do Parchaar.
There were some advantages of this style of singing but there are also many disadvantages:
1. At one time it had the potential to take over real Kirtan - singing of praises of Vaheguru through Gurbani.
2. It reduces the importance of Gurbani particularly when uneducated and uninformed people refer to Dhaarna singing as Kirtan. At best, Dhaarna can be equated with Dhaadi Vaar or Kavishri but never with Amrit Kirtan of Amrit Gurbani.
3. Dhaarna involves singing on pattern of Gurbani Kirtan but of man-made poems. If Dhaarna form of singing is accepted then what is there to stop future Sikh converts in foreign lands to start singing poems of their local languages and then calling it Kirtan? There could be Dhaarna kind of singing in Tamil, Chinese, English, French.
4. Singing of Kachi Baani i.e. man-made poems is not Kalyaankaari like Gurbani is. Gurbani has Paaras Kala which means that just by singing Gurbani, one can get Param-gatt.
At one point, perhaps, singing Dhaarna was good but today it should be stopped altogether. With little attempt, most people can understand Gurbani. Sometimes it seems so ridiculous when they sing their own man-made poems that are translations of very easy Gurbani Pankitis e.g. instead of singing Sadho Man ka Maan Tyaago|| they would sing something like Man da Maan chhadd de oye Saadha|| What's the point of singing Dhaarna in this case, when the original Baani is so easy to understand?
For hundreds of years, Sikhs continued to sing Gurbani alone (or acceptable Baani e.g. Bhai Gurdaas jee's Vaars); what's the need to change this and start singing Dhaarna now?
Kulbir Singh
ਸਤਿਗੁਰਬਚਨਕਮਾਵਣੇਸਚਾਏਹੁਵੀਚਾਰੁ॥
