The best recordings are realized when you capture the dynamics, feel and magic of musicians playing together. A problem arises when attempting to isolate the instruments so that you can control the various sounds during the mix process. In a perfect world, one would isolate each instrument by placing the musician inside an isolation booth. Voice is often recorded in an isolation booth for this same reason.
Large studios have often employed isolation rooms to control the drums from spilling into the bass microphone or vice-versa. Although this works, the sound inside a small iso-booth is not always ideal. Drums and bass sound better when recorded in larger rooms with ambiance. Larger spaces give the low frequencies room to develop. And the very fact that you put glass between the musicians does make a difference. There is something organic that occurs when great players vibe together in the same acoustic space.
A common approach is to set up gobos between instruments to create sound dividers. Although not as ‘perfect’ as isolation rooms, gobos reduce spill while allowing the musicians to perform in the same room. Gobos or ‘go-betweens’ serve two primary functions: they help control sound from spilling between instruments and if properly designed, they do not cause acoustical problems such as early reflections and phase cancellation for the instruments they are serving.
Up until recently, pretty much all recording was done in professional studios. Because a studio would maybe employ 6 to 8 gobos, the market was relatively limited. This is one of the main reasons that finding good quality yet reasonably affordable off-the-shelf gobos has been difficult. So for years, studios have had no choice but to get their gobos made by local carpenters. If designed properly, home made gobos can work well, but you do have to cover all of the bases…