There are a number of works that may be helpful for interpretation, diction, and other subjects related to singing. Many of these books can be found under the subject heading, Singing. Here are a few examples:

 

Singing--Diction

Singing--Instruction and study

Singing--Interpretation (Phrasing, dynamics, etc.)

Bernac, Pierre.
The Interpretation of French Song. NewYork: W.W. Norton, 1978.Ref MT892.B4 1978
Castel, Nico.
A Singer's Manual of Spanish Lyric Diction. New York: Excalibur, 1994. MT883 .C27 1994
Coffin, Berton, ed., [et al.].
Phonetic Readings of Songs and Arias. 2nd ed., with rev. German transcriptions. Metuchen, N.J.: Scarecrow Press, 1982. Ref. MT883.P5 1982
Colorni, Evelina.
Singers' Italian: A Manual of Diction and Phonetics. New York: G. Schirmer, 1970. MT883.C64
Copeman, Harold.
Singing in Latin, or, Pronunciation Explor'd. Oxford : H. Copeman, 1990. MT883 .C65 1990
Emmons, Shirlee, and Stanley Sonntag.
The Art of the Song Recital. New York: G. Schirmer, 1979. Ref MT892.E54 1979
Grubb, Thomas.
Singing in French: A Manual of French Diction and French Vocal Repertoire. New York: Schirmer Books, 1979. MT883.G88
Lehmann, Lotte.
Eighteen Song Cycles: Studies in Their Interpretation. London: Cassell, 1971. MT892.L44 1971
Moore, Gerald.
The Unashamed Accompanist. Rev. and augmented ed. London: Methuen, 1969. MT68.M6
Odom, William.
German for Singers: A Textbook of Diction and Phonetics. New York: Schirmer Books, 1981. MT883.O35
Uris, Dorothy.
To Sing in English: A Guide to Improved Diction. New York: Boosey and Hawkes, 1971. MT883 .U75 1971