I received a comment recently about a vocal recording where the singer would regularly pronounce 'stand' as 'stan', among a host of other dropped final consonants. 'D' and 't' are very common, as is the final 'g' of '-ing'.
The question is whether this is the right thing to do, or should a singer's pronunciation be more precise?
The answer mostly depends on the style of the song. There are some songs where the lyrics are vitally important and if the listener can't make out the words clearly, then the value of the song is lost. In such a case, it will be important that every syllable, and every final consonant, is clearly intelligible.
In other songs, it's the overall feeling that is most important. Being over-precise with pronunciation can sometimes get in the way of delivering the essence of the song to the listener.
The decision on whether to be relaxed or precise isn't something that ends with the singer. It is the producer who is responsible for delivering a marketable product to the record label. The producer is responsible for everything that is achievable within the budget allocated for the project.
The producer should have ears for all that happens in the studio, and the final consonants of words is just one out of a thousand issues that must be considered.
So, if a producer thinks that certain final consonants are being dropped when they shouldn't be, he needs to point this out to the singer. If the singer is being over-precise, then the producer needs to indicate that they can relax a little.
Bear in mind however that singers sometimes perform best in their natural way, and trying to get them to sing in a different way can be detrimental to their overall performance. It may be therefore that although the producer would like to hear those final consonants, he decides to keep quiet on the issue in the interests of getting a better all-round delivery.