One can count on Opera Lafayette to choose lesser-known but worthwhile music and to perform it beautifully. This was true Monday night in the Kennedy Center Terrace Theater, when it performed an assortment of French and Italian music for solos and duets, featuring two of the ensemble’s favorite guest singers.

Soprano Gaële Le Roi and tenor Jean-Paul Fouchécourt were sympathetically matched in the duets, such as the lovely “Qu’il sait peu son malheur” from Lully’s “Atys,” two never-overbearing voices that blended with and supported each other.

Fouchécourt was at his best in the comic solos, camping it up in the cross-dressed role of the old nurse Berenice, in excerpts from Cavalli’s “Ipermestra,” an opera rediscovered at the Utrecht Early Music Festival in 2006. Le Roi, who is a formidable singing actress, excelled in the dramatic recitatives for Galatea, bewailing the death of Acis in “La Galatea” by Loreto Vittori.

Neither singer sounded in top vocal form, with some constriction leading to flatness for Le Roi and top notes that faltered awkwardly into head voice for Fouchécourt, but the overall musicality of phrasing and clarity of diction were impeccable.

Along the way were many charming discoveries, not least the airs de cour of Michel Lambert, a talented and undervalued composer who happened to be Lully’s father-in-law. Lambert’s gorgeous “Vos mepris,” over a repeating bass pattern, was strikingly similar to “Pur ti miro, pur ti godo,” the duet that concludes Monteverdi’s opera “L’Incoronazione di Poppea,” which may not actually be the work of Monteverdi. Happily, that very piece was then offered as the encore, one of the highlights of the evening.

The strongest instrumental accompaniment came from the subtle and varied continuo realization of Scott Pauley on the theorbo and baroque guitar, adding attractive connecting flourishes that anticipated motifs heard in the vocal solos. Ensemble disagreements between cello and harpsichord were too frequent, and the twin violins suffered at times from tuning discrepancies.

Downey is a freelance writer.