What does "ingenuous" mean?

Solution 1:

It is an unusual adjective. In this case, it probably means "undisingenuous" — not attempting, or attempting to appear, to be something she isn't (so "honest" works for "ingenuous").

The "innocent and unsuspecting" is mirrored in the borrowed French noun ingénu(e) (innocent, virtuous, candid, lacking cunning...)

Solution 2:

Here is yet another from M-W:

1 free from any intent to deceive or impress others
ex: photographs that capture the ingenuous smiles of young children at play

Synonyms: artless, genuine, honest, innocent, naive (or na{iuml}ve), natural, real, simple, sincere, true, unaffected, unpretending, unpretentious

Solo voice recital requires more than singing. I took voice for several years and was taught that premeditated physical expression (acting, basically) is equally important to proper projection and economy of breath in order to fully express a piece's narrative.

In the given context

2 As well as the standard oratorio repertory, she sang solo recitals, her dazzling smile and enchantingly ingenuous personality creating an instant bond with audiences.

the synonyms I've made bold-face are those that speak to me with regard to what I was taught.

Solution 3:

The writer is using ingenuous in the sense of ingenue:

ingenue, noun : 1 a : an ingenuous unsophisticated girl or young woman : a girl just entering society : DEBUTANTE {suitable dress for an ingenue}; especially : a stage part representing a character that is youthful, innocent, appealing, sweet, sympathetic {musical comedy ingenue}

Note especially the last sense of Merriam-Webster's definition.