The instruments available for the brass section of the score for my musical are: two trumpets (one doubling on flugelhorn), tenor trombone, bass trombone, and French Horn. I'm thinking that I might like to emulate the sound of two French Horns played softly, in a couple of places. (As there really aren't many places where I would need that type of sound, it's hard to justify the need for another brass instrument).
In experimenting with JABB, I have found that the French Horn played with the flugelhorn a low volume sounds a lot like two horns in their mid-high range. One horn plus a trumpet with a bucket mute also sounds fairly good for the low range. For approximating the sound of low horns, one French Horn + one trombone (open or with a bucket mute) played softly seems to work. So does one horn + bassoon, or one horn + clarinet, depending on the range. But the reeds aren't usually available when I want to do this. I also have an old library of solo Euphonium samples at my disposal. Perhaps the tenor trombonist doubling on Euphonium + French Horn is a better way to go.
I am just wondering if anyone has ever had to do this with real instruments and, if so, which sounds most convincing.