This post is my notes from a more detailed write up from the "Mimic Method" which comes with visual and audio aids. This only contains information on monophthongs - details of diphthongs and triphthongs and will come in a future part in this series.
There are five vowel sounds, and the alphabetic letters are the same as their corresponding phonetic letter [a] [e] [i] [o] [u].
One of the main differences between the Spanish vowels and their English equivalents is that the Spanish vowels are "short and crisp." They do not glide/change to a different sound as you say them. If you put your lips/mouth in the correction position, hold them there, and then perform a voiced sound1, you will get the right sound without having to alter the initial articulation. This is in contrast to some English vowels, like the o in "no" which glides something like a "w" as you say it.
A - The tongue is low and center, lips unrounded. You need to draw your tongue/jaw lower than when you make the ah sound in English words (like pot)
E - The tongue is at middle height and forward, lips unrounded. Be careful not to glide it to a y as we do in many English words such as "hey" and "bay".
I - The tongue is high and forward, lips unrounded. It is pronounced like the e's in the English word see.
O - The tongue is back and center, lips rounded.2
U - The tongue is back and high, lips rounded. Once again make sure not to curl the lips while saying the vowel.
Common Gringo Mistakes:
1. Closing/reducing/changing vowels: A, O, E. Each of the five (lone) vowels sound the same no matter where they are located in a word. When a gringo says nada they may say nah-duh. But the correct pronunciation has the A vowel the same both before and after the d.
2. Gliding vowels. Vowels (by themselves) in Spanish are never diphthongs. They are short sounds with an articulation that remains constant.
3. Lip rounding of vowels. Don't have your o's and u's morph to w's, like they do in the English for the words "no" and "Sue".
- release air through your lungs while "vibrating" your throat, as one always does when making a vowel. [↩]
- The lips being rounded is not all that important since the vowel is defined by the tongue position. You certainly shouldn't have your lips rounding as you say the word, as mentioned before with the word "no" [↩]