I know that when I discussed this in the past, the members of this forum advised me to master writing clearly before trying to write poetically. And I know that is something I need to do. But I want to ask the question anyway: How does one go about emulating other voices and mastering prose rhythm? How does one absorb the rhythms found in other works, and write in rhythms that agree with them? I know that many writers in the past have imitated writers before them and then emerged with their own style. I want to create a new voice that is rich in poetic cadences, but I think in order to do that I need to master prosody in prose. What do you suggest?
I don't bother to emulate the actual speech itself. I usually give the reader a sense of how the character sounds with the following. Hilton was not at his home. 'Gone to London,' said his cleaning lady. She pronounced it Landan. or 'What's it all about?' She asked. Warts it all abaaht? She was squat, ruddy faced. She leant on the fence looking over at him lustily.
Reading, and studying what you read. The reading part is easy, obviously, but if you're looking at style, you should try to keep yourself from getting caught up in the plot or characterization. Break down the words that are used. Try to imagine you're the writer's editor, searching for ways to improve the work. Change a few words and see what it does to the rhythm of the piece. Write the prose words down with line breaks as if it were a poem and see how the structure shows itself. Replace the words in a good paragraph with nonsense syllables and read them out loud, trying to catch the beats. etc. The idea is to really break the writing down and see how it works. Then try your own piece in a similar style. Maybe only a few paragraphs, since you're working with it so intensely. Do the editing, read it out loud, change words, etc. Plot is big, characterization is medium, style comes from the small. The details. You need to really spend some time with them.
I listen to it in my head. Repeat it and hear the rhythm. Reading poetry and noticing the beats probably helps Pay attention to the stresses on each word etc. I'm not entirely sure as it just comes naturally to me. I tend to trust my gut, as it were. I say "comes naturally" but that's obviously not true - I learnt it somewhere along the way because I didn't always write with a sense of rhythm. You just kinda learn to "listen" to your prose. And sometimes the gut tells you to stop here, or add a syllable there, and you do it and play around and see if it's better I tend to do this with descriptions. I don't do this for all 80k words in every draft lol.
Become a musician. Learn to play music and you'll understand rhythm in any form - musical rhythm or prose rhythm. Especially, learn to play music when you're young - preferably as a preteen. It bends your brain in the right way. If you didn't learn music when you were young, you've got a lot of work to do. Sing lots. Writing well is, in a way, singing.
I didn't learn music when I was young and my sense of rhythm is fine... But then I grew up listening to my sister play the piano and violin around the house, and we used to sing Disney songs together.
I didn't say learning to play an instrument is necessary - lots of people have good rhythm without doing that. But the OP is asking how to get a sense of rhythm - he wouldn't ask that if he thought his sense of rhythm was already fine. I just offered a suggestion for how to improve rhythm if he doesn't already have it. (I have to admit that I think it's best to do this when you're young. An adult may have a much harder time learning it.)