Please speak in a friendly tone.

请用友好的语气讲话。

You should also remember to smile as you speak, and use a friendly tone(语调).

你也应该记得说话时面带微笑，并使用友好的语气。

The friendly tone of the meeting is conducive to finding a solution to the problem.

会议友好的气氛有助于找到解决问题的办法。

I was pleased with my friendly tone.

我对自己友好的语调非常满意。

Speak clear and slowly, and maintain friendly tone and pitch.

讲话慢而清晰，保持友好的语调。