Diphthong means, very simply, two vowel sounds.
Example: Although the word "I" (as in "I am") is the vowel "I", is is audibly or phonetically sounded as:
Ah and ee = two phonetic vowel sounds.
Being able to identify diphthongs is crucial in singing because you need to know which vowels you are singing on, and whether they are GOOD VOWEL SOUNDS OR NAUGHTY VOWEL SOUNDS (read more here).
Exercise: When you are singing, listen out for these tricksy diphthongs:
EY EE as in "Maybe."
EYE EE as in "Bite."
EEE UH as in "Ear.'
UH OO as in "Bone."
O EE as in "Boy."
A OU as in "House."
AAH EE as in "Time."
So, when singing a diphthong, which vowel sound should you sing on? The first? The second? Both?
There is no hard and fast rule. You should probably try all the options and decide yourself but, my advice is usually that the first vowel sound is more open.
If this is the case then sing the first vowel sound and use the second vowel to tie up the note, like a full stop.
Time is sung TAAAAAAAAAAAH (eem)
I is sung AAAAAAAAAH (eem)
Bone is sung BOOOOOOOOOOH (oon)
Good luck and let me know how you get on!
,This is my very simple, no nonsense, rule to vowels when singing.
The ones crossed out in the picture are NAUGHTY VOWELS SOUNDS. They make the acoustic space inside your mouth detrimental to singing well: they raise the tongue root, push from the throat, tighten the jaw. They are very, very NAUGHTY.
The ones of the right side of the list are GOOD VOWELS SOUNDSand conducive to singing well. They encourage the top of your mouth (soft palate) to lift, they don't encourage tongue tension or pushing, they open up the mouth (pharynx) and throat, and loosen the jaw.
IMPORTANT NOTE: When I say vowels, I mean phonetic vowels, the sound of them not the vowels as you learn in school.
Exercise: Sing your songs through, circling the NAUGHTY VOWEL SOUNDS and make them GOOD VOWEL SOUNDS.
Tip: Sing the naughty vowels and drop your jaw. It will usually transform them into good vowels.
Let me know how you get on or if you have any questions.
Any smarty pants out there who note that some vowels are diphthongs (double vowel sounds). Yes, you're right. For more on diphthongs, take a read here.
Your mouth is an acoustic chamber and makes as much difference to your sound as singing in a grand echoey cathedral or a small squashy carpeted curtained room.
To encourage you to make the most conducive space in your mouth for singing, I could demand the following:
Raise your soft palate!
Relax your tongue root!
Open your throat!
Loosen your jaw!
Or, I could ask you to use your imagination to do the following:
Imagine an egg. A very special egg that you don't want to break. Maybe inside the egg is a baby chick, or a baby dinosaur?
Put the egg in your mouth.
The point is to encourage you to make as much space as you can in the internal area of your mouth so that, as the sound passes through, it can ricochet around, growing in lovely warm resonance rather than being swallowed up and absorbed.
The feeling and imagery of having an egg inside your mouth when you sing keeps your tongue flat at the root base, the roof of your mouth (soft palate) high, your jaw loose and your throat open.
For other tips about using the resonating chamber of the mouth (pharynx) have a read of:
Good Vowel Naughty vowel
The golden golf ball
Let me know if the egg imagery works for you!