The Khalsa is the body of the Guru and Gurbani (Guru Granth Sahib Ji) is the essence. Without Gurbani the Khalsa is not entitled to the status of Guru.
Dr. Kharak Singh in Guru Panth-Granth further explains:

“In the twin doctrine of 'Guru Granth – Guru Panth', the two components have a complementary relationship with a distinct role assigned to each. For effective functioning of body and soul, they have to act together. In practice the doctrine means that the body of the Panth has to take decisions on temporal matters dealing with a situation prevailing at a particular time strictly following the spiritual principles laid down in Guru Granth Sahib to carry out the will of God or sarbat da bhala.”
 

As such Akal Takht Sahib became the capital building or throne of the Khalsa Panth collectively alongside Guru Granth Sahib. Guru Granth Sahib is absolute sovereign/independent leader of the Sikhs and the Khalsa’s job is to protect Guru Granth Sahib, respond to situations/conflicts as the physical arm of the Guru collectively, and create new ideas based on the teachings of Guru Granth Sahib Ji. 

In order to collectively organize and make decisions the Khalsa assembled at Akal Takht to conduct a Sarbat Khalsa (literally all Khalsa assembly). The Sarbat Khalsa is a unique democratic Sikh system of democracy based on consensus (common minimum program) as opposed to western majority rules democracy. 

There have been many times in Sikh history where the Khalsa has not had access to Akal Takht Sahib due to corruption or malicious government forces. During these times the Khalsa would conduct a Sarbat Khalsa in places they could freely meet without outside interference.

Ordinarily the Khalsa proposed to meet at Akal Takht twice a year during the Baisakhi and Diwali festivals which were the opportune times for such meetings when farmers were able to leave their crops unattended. On the occasions of the fairs and festivals the Sarbat Khalsa would discuss the problems that confronted the Sikh Nation. The Khalsa would also call emergency Sarbat Khalsa’s to discuss topics of immense political importance or understand out to counter an imminent danger to any innocent people. One example of Sarbat Khalsa: When Tara Singh Van was killed in 1726 along with his companions (the entire sangat managing Darbar Sahib), the Sikhs met at Akal Takht and decided to declare war against the government by destabilizing it.

 
According to John Malcolm, 
“When the chiefs meet upon this solemn occasion, it is concluded that all private animosities cease and that every man sacrifices his personal feelings at the shrine of general good and actuated by the principles of pure patriotism thinks of nothing but the interests of the religion and commonwealth to which he belongs.”
 

Thus sitting in front of Guru Granth Sahib at Akal Takht, they proceeded to consider the danger with which they were threatened. They settled their plans and strategy for averting the danger and chose the generals who were to lead their armies against the offenders.

As the Sikh Sardars held Akal Takht in high esteem the decisions taken there had a moral and religious binding on them. The Sardars could not, therefore, afford to go against the decisions taken at Akal Takht, and run the risk of losing their popularity with the community. Though the Sardars, at times, quarreled among themselves, all was peace and friendship when they met at Akal Takht because it was not about their personal wants it was about the Khalsa and the Guru.

At the time of their meeting, they assembled in the open space in front of Akal Takht. Each Sardar had his companions sitting behind him and he participated in the deliberations on behalf of his men. If the followers had any point to make, they did it through their Sardar or they could do it direct. It was not Sardars' assembly nor where the deliberations of the national problems the monopoly of the chiefs. But it was a gathering of the community. According to Fauja Singh, in the assembly at Akal Takht the basic ideas kept before them by its members were those of equality, unanimity and responsibility. The idea of equality and principles of Sangat from Guru Granth Sahib entitled every member of the Nation, including women, to attend and participate in the discussions. The right of participation in discussions had to be exercised personally and directly and not through elected or nominated representatives. The principle of unanimity was based on the belief that the Khalsa was the embodiment of the Holy Guru and that all their assemblies were made Sanctimonious by the Guru's presence in them. Therefore, all collective deliberations were conducted in a detached manner. Different viewpoints could be expressed but as they were bound by a solemn pledge of being united in the presence of the Guru, the resolutions were passed only unanimously.
 

The councils of the Sarbat Khalsa meeting at Akal Takht had a variety of problems for their deliberations. It was there that the Sarbat Khalsa selected the Jathedar or the chief leader of the Dal Khalsa. They also chose agents who were entrusted with powers to negotiate with others on behalf of the Sikh Nation. Sometimes cases of disputed successions were brought up for its verdict as Sarbat Khalsa acted as a judicial body. At Sarbat Khalsa they also took measures for the spread of the Sikh faith and the management of the Guruduaras. Throughout the 18th century, Akal Takht was the hub of the Sikh politics and it gave direction to the activities of the people through resolutions passed there.
 

The assembly of the Sikh chiefs at Akal Takht cannot be called the Central Government of the Sikh Misls. This assembly had no political jurisdiction or military sanction over the individual chiefs, nor was it necessary. Their attendance was not compulsory but the chiefs considered it obligatory to attend specially with a view to promoting their own interests. Although there existed no means to enforce an obedience to the Gurmatta passed at Akal Takht, yet there was never an occasion known when such a decision was flouted. The decisions taken in the presence of Guru Granth Sahib had behind them the Gurus sanction which was greater in force than that of any power of Earth. The Sikhs obeyed the decisions of Akal Takht even at the cost of their lives. The simple practice and moral authority of the Akal Takht were sufficient to preserve the Khalsa in the troublous times in the 18th century and beyond.
 

When the situation on all fronts eased, the Sikh chiefs became a little indifferent to attend the meetings of the Sarbat Khalsa at Akal Takht. Now their meetings were attended only by a few chiefs. But the absentees never meant any opposition to such meetings or any resistance to decisions taken there. Being busy in their internal affairs, the Sardars, sometimes, just could not attend. There was absolutely no such thing as intentional breaking away of the Sardars from Akal Takht with a calculated design to weaken this seat of authority. With the rise of Ranjit Singh as a sovereign ruler, the Punjab came to be consolidated and the foreign invaders ceased to endanger the country and the community. So during Ranjit Singh's period the rule of Akal Takht fell into disuse so far as political affairs were concerned. Nobody could be above the decisions taken at this place, not even the great Maharaja. The predominant opinion is that Ranjit Singh paid his homage to Akal Takht not simply as a force which he could not afford to ignore but as the ultimate source of strength and stability to the state he was engaged to build. Others have the opinion Ranjit Singh maliciously took steps to ensure the democratic structure of Sarbat Khalsa was not used anymore in order to stay in power.