Jo-Ral Straight French Horn MuteJo Ral aluminum French Horn straight mute model FRA. This model is also available in copper (FRC). With a delightfully more mellow finish than traditional aluminum models, the All Copper French Horn Straight Mute allows for a free blowing sound in all registers, providing a consistent flow quality that allows musicians to achieve a delicate, controlled sound without transposing registers. The Jo Ral FRC All Copper Non Transposing French Horn Straight