In this circuit a single LM324 op-amp package provides 3 CV booster amps and an alternative to the Velocity sensitive Gate signal of a stock Tmax. The new Volume Gate is based on the volume hand's position, not it's change in position, an easier skill to master. Probably so, the Velocity sensitive Gate takes some practice to master. For best results the Tmax should be tuned to Controller Mode, as detailed in its manual. Remember that this Gate responds to changes in Volume hand position.
Sensitivity is adjustable with the front panel Velocity control.
At lower Velocity settings your hand must approach the Volume antenna more quickly to turn on the Gate, at higher settings very slow motions produce results. Constant motion toward the antenna is necessary to hold the gate on, it turns off shortly after motions stops or if you begin to withdraw your hand. This is very predictable and easy to control - once set, the Gate stays set until you rmove your hand. The illustration is largely self-explanatory. Wire the top and bottom lugs of the switch to lug 2 of R83 and lug 2 of R84 respectively.