Probably the biggest difference between the straight and the curved soprano sax is in how it projects sound. The straight sax thrusts the music out at the audience, while the curved instrument projects it upward. Consequently, the musician may hear himself better with the curved sax, but the audience hears the straight sax better. But there's a trade-off. The straight sax usually requires two microphones, one at the bell and one near the keys. This is sometimes mitigated by clipping a specially made double mike across the bell of the instrument. The curved model only requires a single microphone, as it will pick up sound from the bell and the keys.
While neither sax has the tone of a larger sax--the soprano is tuned an octave higher than the tenor saxophone--the straight soprano has a more nasal, metal-edged sound than the curved version, making the straight sax sound more like an oboe. John Coltrane used this tone to great effect in his recording of "My Favorite Things," giving it a Middle Eastern flavor.
Many saxophone players say it is more difficult to keep a curved soprano in tune than a straight one.
The musician holds the curved saxophone closer to her body, so she doesn't have to reach out to work the keys. However, the keys on a curved saxophone are more crowded. The straight sax is more tiring, because the sax player has to hold the instrument up with outstretched arms rather than letting the neck strap do the work. The straight sax is better when played while standing up. Both instruments are hard to play; though less breath is required to produce sound, the reed action on the smaller instrument is stiffer, and it takes strong lip muscles to produce a sound.
Adolphe Sax, who invented the instrument in the 1840s, produced several instruments to cover tonal ranges from contrabass to sopranino. The original soprano saxes had a straight body; the curved sopranos became popular in the 1920s but eventually faded out. Though the curved model made a comeback in the late 20th century, the straight version remains the most popular.
Soprano saxophone is a niche instrument in music, as tenor and alto sax have a deeper, warmer tone and are easier to play. But several players used soprano sax to create their own sound. Coltrane, Sidney Bechet, Steve Lacy and Wayne Shorter used the instrument extensively in jazz, while Kenny G made a name for himself in pop. All of these musicians preferred the straight soprano to the curved version.