The first links are to Malcomb McNab's great work:
Malcolm's solos were recorded using two
microphones simultaneously; an RCA KU-3A ribbon mic (circa 1950) 2 feet
away, and the Royer SF-24. Because the SF-24 was so much of the
orchestra sound, keeping it up for ambiance on Malcolm's trumpet
overdubs maintained the acoustical environment common to all of the
other tracks, giving the illusion of Malcolm standing in front of the
orchestra and playing together with them. In the mix, Malcolm's trumpet
balance was about 60% RCA - 40% SF-24. -Gary Grant - Royer Labs