type !voice <voice name> to change your TTS voice

Example:

!voice Microsoft Ichiro

Available voices: Microsoft David Desktop, Microsoft Naayf, Microsoft Ivan, Microsoft Herena, Microsoft Jakub, Microsoft Helle, Microsoft Michael, Microsoft Karsten, Microsoft Hedda, Microsoft Katja, Microsoft Stefan, Microsoft Stefanos, Microsoft Catherine, Microsoft James, Microsoft Linda, Microsoft Richard, Microsoft George, Microsoft Hazel, Microsoft Susan, Microsoft Sean, Microsoft Heera, Microsoft Ravi, Microsoft David, Microsoft Mark, Microsoft Zira, Microsoft Helena, Microsoft Laura, Microsoft Pablo, Microsoft Raul, Microsoft Sabina, Microsoft Heidi, Microsoft Caroline, Microsoft Claude, Microsoft Nathalie(Canada), Microsoft Guillaume, Microsoft Hortense, Microsoft Julie, Microsoft Paul, Microsoft Asaf, Microsoft Hemant, Microsoft Kalpana, Microsoft Matej, Microsoft Szabolcs, Microsoft Andika, Microsoft Cosimo, Microsoft Elsa, Microsoft Ayumi, Microsoft Haruka, Microsoft Ichiro, Microsoft Sayaka, Microsoft Heami, Microsoft Rizwan, Microsoft Jon, Microsoft Bart, Microsoft Frank, Microsoft Adam, Microsoft Paulina, Microsoft Daniel, Microsoft Maria, Microsoft Helia, Microsoft Andrei, Microsoft Irina, Microsoft Pavel, Microsoft Filip, Microsoft Lado, Microsoft Bengt, Microsoft Valluvar, Microsoft Pattara, Microsoft Tolga, Microsoft An, Microsoft Huihui, Microsoft Kangkang, Microsoft Yaoyao, Microsoft Danny, Microsoft Tracy, Microsoft Hanhan, Microsoft Yating, Microsoft Zhiwei, Microsoft Hedda Desktop, Microsoft Hazel Desktop, Microsoft Hoda, Microsoft Zira Desktop, Microsoft Helena Desktop, Microsoft Sabina Desktop, Microsoft Hortense Desktop, Microsoft Elsa Desktop, Microsoft Haruka Desktop, Microsoft Heami Desktop, Microsoft Paulina Desktop, Microsoft Maria Desktop, Microsoft Irina Desktop, Microsoft Huihui Desktop, Microsoft Tracy Desktop

List of Microsoft Voices

More voices: choose the name of the voice from the dropdown at https://responsivevoice.org