4.4 Timbre irregularities: nasal, recessed sound, "white sound"
If the palate is slightly raised, a channel forms in the nasopharynx, the length of what is such that it absorbs frequencies of about 2000 Hz, and our ear perceives their absence so that it sound to us as a nasal sound. To eliminate this defect, work on functioning of the soft palate. A similar technique can be applied if you notice "white" singing, i.e. your sound is formed too close. Exercises with the vowels OU and O adding consonants K and D formed in the pharyngeal cavity can also be helpful in this case. The problem with the recessed sound can be fixed with doing the exercises containing some combinations of closely pronounced consonants and vowels like NI, ZEE, DI, ZA etc.