The MIDI channel strips work as a remote control for the mixing parameters of the controlled sound modules and synthesizers (volume and pan, for example).
If your sound source understands bank select events, you can choose the bank number with the Bank parameter field at the bottom of each channel strip (only visible if the Bank parameter in the Object inspector is selected). Remember that not all synthesizers support bank select events. You can use several different bank select formats (see Mapped instrument objects overview).
The Program button allows you to select a sound by name. Click it to open a pop-up menu that contains all GM sound names. Each channel has its own pop-up menu.
The Volume fader controls the output level of a MIDI channel. Adjusting it sends controller 7 via your MIDI interface.
The Mute button switches the volume of the channel between zero and the current Volume fader position. In practice, this means that if the button is selected, the channel is muted. If you deselect the button, the current Volume fader position (and value) is used.
You can assign any controller to each of the knobs.
In addition to the GM Standard, there are extended standards created by Roland (GS) and Yamaha (XG). GS and XG mode allow you to select different effect programs, and to control the level of the reverb and chorus effects.
The Reset button transmits a GS On or XG On command, and resets all controllers to neutral positions. This allows you to reset all connected sound modules to their standard settings, and begin a mix from scratch.
Drag the Volume fader up or down.
Click the Mute button.
Click the label next to the knob.
Choose the controller you want from the pop-up menu that appears.
Open the Logic Pro Mixer, then choose GS/XG Effect Controls from the Mixer menu bar.
The GS/XG configuration control is displayed in the upper-right corner of the Mixer, allowing you to select different effect programs.
Choose the standard you want from the first pop-up menu in the upper-right corner of the Logic Pro Mixer.
Depending on your selection, the controllers for the extended effects appear.
Choose the reverb or chorus effect from the second pop-up menu.
Program the reverb or delay time by double-clicking the Time parameter, then entering a value in the input field.