Tone in an essay is similar to the tone in a conversation. When conversing, you adopt different tones and speaking styles depending on the context in which you are speaking and on the person who you are speaking to. In the same way, a writer chooses a tone that is suitable to the topic of the essay and to the audience for whom he is writing. Tone sets the stage for the thoughts and ideas that are presented in an essay. It also reveals the writer's attitude about the topic.
Consider the context and situation the essay addresses. Essays are written for a variety of purposes. The goal of the essay may be to commemorate an important event, to honor a particular person's achievement, to motivate a particular group or to address a political or social issue. A light-hearted tone may work well in one context, but it may be inappropriate or offensive in a different setting.
Write for the audience. It is important to keep the particular audience in mind as this affects the tone of the essay. For example, the appropriate tone for a political essay depends upon the group being addressed. One group may respond better to political sarcasm and humor, whereas another group may be more receptive to a formal, serious tone.
Select a writing style appropriate to the subject matter. A formal writing style is generally impersonal and objective. An informal style tends to be subjective and personal, causal and plainspoken. If the subject matter is academic or somber, a serious and formal tone is appropriate. If the essay topic is celebratory, a festive, joyous and informal tone is more suitable.