Yamaha O2R Owner's Manual page 261

Solo Safe – Tape, Mic, Line, and Effects – These functions disable solo
l
On/Off selection. If you set a channel to Solo Safe while it was set to
Solo ON, the channel remains unconditionally ON in "Mixdown
Mode" when you select Solo.
This function has no effect in "Recording Mode".
How to use Solo
1. Press the (SOLO) button.
The LEDs inset in all the [ON] buttons start flashing.
2. Press the (ON) buttons for the channels you want to solo.
The LED inset in the [ON] button you select is illuminated steadily. If you
selected "Last Solo" in the Status command, only the last channel you
select will be soloed.
3. Press the (SOLO) button again to cancel the solo function.
The 02R will remember the channel(s) you selected for solo. If you press the
[SOLO] button again, the previously selected channels will be soloed.
Digital I/O, Setup, and Utilities
Digital Recording Console 02R User's Guide
161