Why so serious? There is nothing cheerful or amusing about the solemn voice. It's the voice your CEO uses when they about to let an employee go. The voice of a lover swearing to always protect his significant other. There is sincerity in it, but sometimes, it can send chills down your spine.
It may be strict and boringly formal, but it is also extremely effective. It goes straight to the point and gets the main message heard with minimal words. There is no beating around the bush with the solemn voice nor is there making jokes mid-sentence. It means business!
If you are making a demo, a digital ad, an explainer video, or anything that should be formal and serious, this is the voice to use. You can also use the solemn voice for digital biographies and autobiographies or audio reading of fervent novels and books. All formal speeches carry this voice, especially those that have been prewritten and are to be read out loud.
It is serious, stern, and is mostly used to show the formality or meaningfulness of the topic being discussed. The solemn voice is proper and very strict in nature and doesn't allow deviations from the tone being used.
Due to the formality of this voice, it often comes with a tense, somewhat uncomfortable atmosphere. It can, however, be used ironically in comedic scripts. Think of a character relaying sad news in a solemn tone, followed by an unexpected, absurd explanation of the news.