A lot of pop singing displays poor enunciation, that is, the words are not clearly articulated and the poem or text is lost, It often takes many hearings to determine the words being sung. Obviously this is being done as a stylistic choice in many cases; in others it is simply inadequate technique and the desire to sing overcomes the need to communicate a textual message.
But in any kind of singing, whether it emphasize text or not, the greatest enunciation difficulties center around the articulation of consonants. Most well articulated consonants divide the sung vocal line into segments. The sung vocal line is created by connecting vowels together in as continuous a pattern as possible.
The secret of keeping a legato or continuous vocal line is to articulate the consonants carefully but not give them sufficient length such that they segment the vowel line into individual, separate tones. Obviously voiced consonants produce less separating of the vowel line than do unvoiced consonants because the vocal tone can continue through the articulation of voiced consonants such as /m/, / n/, /ng/, and even /d/, sometimes /b/ etc. etc.
Unvoiced consonants are a more difficult matter because their very nature is to stop the continuous vowel tone and this causes the sung line to lose some of its legato quality. The general rule for articulation of unvoiced consonants is clarity, but with short duration. The loudness of unvoiced consonants should not greatly exceed the loudness of the sung vowel before and after the consonant and the amount of time the unvoiced consonant occupies should be short enough so the vowel line sounds as continuous as possible.
To put it another way, if the sung vowel line is sufficiently segmented the listener’s mind must make the desired connections of these segments in order to hear what is the obvious legato intent of the song. This is more subconscious mind work than most listeners want and the negative effect is that the listener becomes distracted or bored and the effect of the song is lost.
As a voice teacher and opera director there have been many occasions when I have suggested that a singer be less concerned with the consonants and emphasize the vowel line. It always surprises the singer when fellow singers say they can now understand the words even though the singer feels he/she is emphasizing the words less.
It is all a matter of a well defined technique of articulation that recognizes the causes and effects of singing enunciation.