Gopi Geet is also known as stotra (praise), and this stotra is not only beads of words but an arrangement of one’s emotion..To start with we now know that in Gopi–Geet, Krishna’s Yash (Fame) is clearly demonstrated. Without Aishvarya (wealth) Yash cannot be possible. Yash cannot be spread without it. In Aishvarya one sees that enticement, Madhuriya which flows very well in Gopi–Geet. This quality and its blessed state of addiction is perfectly established in this Geet. To demonstrate this, the Gopis decided that only Indira Chand can perfectly do justice to Krishna’s qualities (kalyana gunas) and beauty( Madhuriya).
What does Indira means? Let us look at the meaning of this word. Indira means the one who bestows the boon with Aishvarya, is known as Indira. The one who donate (daan) Ashvariya, the spiritual wealth. The Lord shows His eagerness to give this daan.
Gopis when hadthe daan of Ashvariya, believed that the only wealth is the Lord Sri Krishna, having Him with them was a reward of Bhakti and Lord was everything to Gopis and no material enticement matched the value of this Ashvariya daan, hence they used Indira Chand.
The second reason:
Krishna resides on the kingdom of Gopis love (emotions), and in Vraj emotions takes the better of offering (Bhog). It is materialistic & only a physical activity, to serve within confined service for a return of the service. To demonstrate that the Lord is independent, that is, He is Unique, Gopis used the Indira Chand.
The third reason:
According to Chand Shastra (the Chronicle that records all Chand), Indira Chand is known by other two different names, these are elegance (Lalit) and orchid (Kanakmanjari). The Gopi–Geet has that elegancy and as it progresses the Geet becomes intoxicating (madak) just like Kanakmanjari, the orchids. So in Gopi–Geet we see the elegancy of love and the intoxication.
Gopi–Geet is sung by Rushi-rupa and Shruty-rupa Gopis, and they were quite knowledgeable about the Indira chand. So this is the reason gopis sang this Gopi–Geet in Indira chand.
Every charan has at least eleven words, which depicts Ekadashi (eleven) indriya of gopis’ sharanagati (surrendered to Krishna). And this was also one of the reasons why at the end of Gopi–Geet, Shree Krishna appeared.
Shree Mahaprabhuji also explained in his Subodhini (Srimad Bhagavatham) on Gopi–Geet about the eleven words stanza. When Gopi had pain of seperation (Virah), Shree Krishna had to take form of Vishnu swaroop to protect them from killing themselves from Virah-Agni (fire that burns the soul in the state of separation). Then in the end, when in the state of Virah, these gopis could not sustain the Virah-Agni and the heart started crying. (Rhudan=crying) and this was a way of cleansing of heart and mind.
The other trick gopis instigated was the rhythm of cry. In Indira chand there is special poetic rules to cry out in poems and stanzas are set to crying rhythms, and these rhythms are called Laghu-Guru arrangements. This Laghu-Guru also explains the style and raga of Indira chand and how to sob at a particular word or at the end of particular stanza. So, in fact, Laghu-Guru is the theme of Virah, a cry for help, a musical melody in which the cry and the sobs are set in a particular style and arrangements, and these arrangements is also known as dhvani yojna. Hence the Lord, Sri Krishna rushes to bestow the spiritual wealth of love (prema) in Gopis heart.