Flûte d'amour
The flûte d'amour (Ital: flauto d'amore, Ger: Liebesflöte, translates as: Love Flute) is pitched in either A or B♭ and is intermediate in size between the modern C concert flute and the alto flute in G. It is the mezzo-soprano member of the flute family. It is also sometimes called a tenor flute.
Unlike the alto flute, the ratio between the bore diameter and tube length is much the same as in the concert flute, which allows it to have a mellower tone colour but without losing any facility in the top octave. Its lowest sounding note is B♭ (or A).[1]
In contrast, the alto flute has a wider bore in relation to its tube length. This is to provide it with extra power in the bottom register, but this causes the alto problems with intonation and facility of sounding some notes in its top register.
Some simple flûtes d'amour were also made in the key of A♭ in the late eighteenth century.
When used in jazz, the B♭ version is usually implemented to complement the tenor saxophone and clarinet, as both are in B♭.