So: You feel you know the sound system and intonation of an accent perfectly, you practice and practice. But you feel you are sliding in and out of the accent, overdoing and undergoing certain sounds features. It just doesn’t feel or sound quite right.
Have you warmed up the voice placement? If the accent isn’t sitting in the correct muscular placement for the accent, or oral posture, it won’t sound or feel quite right. The oral posture around which the sounds are taking place needs to be as relaxed and flexible to be able to speak smoothly with a natural placement and rhythm.
Phonetically the same. Yet so different: Listen to 'sound 1' in the following link in different accents, including British Received Pronunciation, the general American accent, the Canadian accent, Cockney, Irish, Australian accents and more? Click here to listen There is no/ little phonetic change, the phonemes are the same. However depending on the shape, muscularity and tension in the oral cavity, placements for different accents can make the same word even with the same phonemes sound very different.
Changing shape: When speech is created by voice, it is shaped and compressed as it resonates through the oral cavity to produce phonemes and words. So every accent and language you learn as a non-native speaker requires a different shape in the oral posture. Interestingly, some accents lend themselves to others in this way making it relatively easy to achieve the correct oral posture for an accent, where as others are the opposite and make it tough to get the correct and comfortable voice placement for the target accent. Depending which accent you are learning, sometimes it’s easier to transfer placement from one accent but not from another. For example; Australian easily lends itself to the American accent but not so much to British RP. Yet interestingly, often Americans find it harder to do an Australian accent well. Why is this? Possibly it could be that in the Australian accent, the degree of nasality and voice placement are generally further back than in the American accent, but as they also have similaritles, coupled with the fact that certain features such as the ‘dark L’ in all environments are persistent throughout, their similarities are so close that it’s harder to pick out the subtle differences and strike a balance.
So where to start? One great way to start is to say / hum the consonant /m/ ‘mmm’ to warm up. You can practice sending the ‘mmm’ to different areas of the mouth and head; it is a long consonant which while produced with the lips and nose, can sound SO different depending on the accent’s placement. Try a long / m /and adjust the tension in the tongue height, soft palate, neck, lips jaw - how does the sound and resonance change as you do this?
Exploring voice placement Try words that are phonetically the same between your own accent and the accent you’re learning. They sound the same phonetically but so different with shifting voice placement. Try saying a vowel sound that is the same between both accents for a long time and adjust the voice placement as you do so.
-British and learning American? Try this: Imagine you have a boiled sweet on top the middle of the tongue (to raise the tongue body height) and are rolling it around between the tongue body and the hard palate to get the mid-tongue muscularity. Keep the tongue body higher that you would than. say, for the neutral British accent.
-American learning British RP? Try this: do: Relax and lower the tongue body and ditch the mid-tongue muscularity. Imagine you are sending the sound into the front mask of the face and that you have two tic-tac sweets between the lower front teeth and lips to help bring the sound placement further forward. Don’t: worry if it feels strange and unfamiliar. Avoid getting overly tense, it will come with practice
-Australian learning Cockney? Australian and Cockney are almost identical phoneticlly, so this is mostly about shifting the voice placement from one to the other: Try yawning to create space in the back of the mouth and to raise the soft palate a little, and imagine you have a boiled sweet under the tongue with a lazy lower jaw. Practice counting out loud from 1 to 10 to experiment with the new voice placement.
-Connect the new accent with your voice: Practice saying a line or two of your script in different emotions, such as assertively, amused, bored, angry, sarcastic etc. What do these bring out in the accent?
-KEEP PRACTICING. IT WILL COME WITH TIME AND DEDICATION :)