Model JK4300-8 Keilwerth Baritone Saxophone SX 90 R:Professional model. The Keilwerth SX 90 baritone saxophone produces a rich, deep tone. It has the capability of blending into a jazz ensemble or cutting through during solos. Adjustable palm keys make the SX 90 baritone saxophone comfortable and easy to play, allowing the musician to concentrate on his performance and not his horn.