The Wolfess: I don't remember having seen anyone ask about this yet, and I'm sure you're not releasing much information about the Ikana region yet, but I was wondering if the Ikana Castle (and its resident talking Stalfos/dancing Redeads) will make an appearance in the opera? Also, will they play a big part or small part if they are included?
Ikana Castle and its king will most definitely make an appearance. He plays an important role, but no longer in duration than that of most denizens of Termina Kafei meets. I don't think his guards will appear, though, neither will the dancing Redeads. Act III is rather focused on the uneasiness of the valley, and having Redeads dance like they do in the game wouldn't fit.
Josef Stylin: Does Odolwa play a big part in the story? Will anybody need to fight him, considering he's an evil force made by Majora? And is he the only boss to appear/be mentioned?
Odolwa is crucial for the giant to be revealed. The Deku end up accidentally confronting Odolwa due to Kafei's intrusion in the monkey's execution. I do think that he is the only boss to appear, especially because no other is either humanoid (for staging purposes) or as easily accessible (Kafei cannot possibly reach Snowhead, for example).
BowserTheSecond: Will Kotake and Koume appear in the play?
I tried! I love their theme and I can hear a duet for their voices fitting it so well! But there is no way that could happen without extending Act I too much for something that isn't even plot-related. Sorry, but Kotake and Koume have to join the unused cast.
Nope. This is from Act II. Kafei passes out after being thoroughly exhausted in the pursuit of another fruitless lead on Sakon, and dreams.
Listen again. The moment Kamaro's Dance is over, Sakon's theme appears in full! So it's not just the end. In fact, the entire dream is riddled with Sakon's theme in all shapes and forms. Kafei is dreaming of his thief, along with other things.
Oscar Suncin: Amazing, Kafei will be a tenor or a baritone? Please let him be a baritone!
Sorry. Kafei's voice is way more suited for tenor. You already heard him sing in Demo #4.