The mezzo-soprano saxophone, sometimes called the F alto saxophone, is an instrument in the saxophone family. It is in the key of F, pitched a whole step above the alto saxophone. Its size and the sound are similar to the E♭ alto, although the upper register sounds more like a B♭ soprano. Very few mezzo-sopranos exist—they were only produced in 1928 and 1929 by the C.G. Conn company. They were not popular and did not sell widely, as their production coincided with the Wall Street Crash of 1929 and the Great Depression. Harsh economic conditions forced Conn to reduce the range of saxophones they produced to the most popular models.
Conn used the surplus stock of mezzo-sopranos to teach instrument repair in Conn's Elkhart workshops. Typically, a Conn instructor would deliberately damage the mezzo-sopranos (e.g. dropping them onto a concrete floor) and the students would then be tasked with repairing them. The repeated wear and tear of these actions eventually destroyed the saxophones.
The mezzo-soprano is the only saxophone pitched in F, apart from a few prototypes of an F baritone saxophone. (Although Maurice Ravel's 1928 orchestral work Boléro calls for a sopranino saxophone in F, it is unlikely that such an instrument ever existed; nowadays the sopranino saxophone part is usually played on a soprano saxophone).
Notable players of the mezzo-soprano saxophone include Anthony Braxton, James Carter, Vinny Golia and Jay Easton.
More recently a mezzo-soprano in the key of G has been produced by Danish woodwind technician Peter Jessen, most notably played by Benjamin Koppel and Joe Lovano. Their collaboration can be heard on "The Mezzo Sax Encounter" (vinyl and CD, 2016) where Koppel and Lovano are accompagnied by pianist Kenny Werner, bassist Scott Colley and Drummer Johnathan Blake. This instrument is more in the timbral quality of Bb soprano saxophone.
It was asked for by Richard Strauss in his Sinfonia Domestica written in 1903-1904, where included in the music are parts for four saxophones including an alto saxophone in F.
On January 28, 2012, Aquilasax of New Zealand, known for producing modern C melody and C soprano saxophones, announced on their Facebook page that they would consider developing a revival of the F mezzo-soprano saxophone if enough customer interest was demonstrated. Aquilasax added a page on their online store for potential buyers to place their names on a waiting list, saying that they would consider proceeding with development of the horn if there was enough response to justify development costs. The listed price of the Aquilasax F-Mezzo-Soprano saxophone, if produced, is $2950.