It is said in Music Parlance : "SRUTHI MAATHA LAYA PITAH'. For any music, be it vocal or instumental, perfect Sruthi allignment is of Utmost Importance to get the real pleasure and melody of the music that is played or sung.
Especially Vocal music students must spend few minutes of their practice session concentrating only in getting their vocal chords perfectly alligned to the sruthi in which they are singing. This exercise has to be done right from the beginning stages so that it becomes a habit.
As far as possible the vocal music students must avoid singing in half-noted sruthis. Instead choose full-noted sruthis like F, G, A (for female students) and B, C, D (for male students) atleast in the beginning stages of learning. This will enable them to get perfect tonal quality. Oncd they get perfection in full notes, they can shift to half-noted sruthis to get volume and weight in their voice.
As Teachers / guides, the role of the GURUs play a very important part, in as much as guiding the students choose their correct sruthi and also in making them attain the required amount of perfection, so that soulful music / singing emanates.