1. The active instrument light shows you which instrument’s parameters you are changing. Click this area on another instrument to change the focus of the controls.
2. The Instrument display features a drop-down for loading that appears when the field is clicked.
3. Ensemble multi-instruments presets. On top of the ones installed with the ARIA products, the user can save his own.
4. Tuning controls help you to build sections without phasing problems.
5. MIDI channel assignment is quick and clear.
6. Stereo output assignment allows you to route instruments on up to 16 unique stereo output channels when GPO 4 runs as a plug-in. The Standalone is limited to a single stereo output.
7. Per-instrument sends let you apply the perfect amount of reverb to each instrument.
8. Mute and Solo buses allow you to mix your compositions better or focus in on a certain part while composing.
9. Graphical faders give you a quick idea of an instrument’s presence in the mix. The faders respond to CC#7 commands.
10. Pan control to place each instrument in the stereo field from left to right.
11. Additional screens give you advanced control over the instrument-specific properties, reverb parameters, and even temperament of the scales.
12. A keyboard shows keyswitches in red, the current keyswitch to the left, and the instrument’s playable range in white.
13. Keyswitch menu. Showing what articulation is selected. Also an alternate way of choosing your keyswitch.
14. The modulation wheel is a representation of the active instrument's cc1 level. It can also be adjusted directly on the interface.
15. Pedals for una corda, sostenuto and sustain(damper). Clickable, but will also respond to midi control.