What is Solo In Place (SIP)?
Normally when using Solo, the channel or channels that are soloed are routed to the Headphone output for monitoring. Solo in Place is different in that only the soloed channels are routed to the Main Mix outputs instead of the headphone output. In this mode, when a channel is soloed, all other channels are muted so that only the soloed channel is heard, in its stereo position, at the console's mix outputs. This is usually used only during soundchecks or rehearsals in live performances. It is also used extensively in recording studio mixing.
How to enable and use SIP
On the Si Mixer
To enable SIP, select Monitor/Solo on the screen.

Scroll down to select Solo In Place, then push down on the encoder to turn On. Notice you will see the red SIP icon in the upper right of screen turn on. This will be the only indication that you are in the SIP mode.

Notice that when you select a Solo on a channel, all other channels will mute, letting you hear the individual channel, where it sits in the stereo image, including all processing. It is a post fader, post processing solo.

WARNING - On Si Mixers, SIP state is saved with the show file. So, it is possible to load a show file that will enable SIP, with the icon on the screen being the only indication.
On the Vi Mixer
To enable SIP, select Setup on the Monitor section of mixer.

Enable SIP by pushing the SIP button on screen.

The only indication of SIP being enabled will be the SIP button highlighted. It is automatically cancelled if the Monitor Setup screen is closed, to ensure that it cannot accidently be left on. IE: to use SIP, you must leave monitor setup open on the control bay screen.

Notice that when you select a Solo on a channel, all other channels will mute, letting you hear the individual channel, where it sits in the stereo image, including all processing. It is a post fader, post processing solo.

On the Ui Mixer
Go to Settings/ Global and look at Solo Routing. Selecting MASTER + HP will essentially enable SIP Solo in Place mode. When you Solo any channel, all others will be muted (with no indication). To be a true SIP, letting you hear the individual channel, where it sits in the stereo image, including all processing, you will also need to set the Solo Type to AFL. This will change it to a post fader, post processing solo.

WARNING - On Ui Mixers, there is no indication that you are in SIP mode. There is the normal “S" on the master readout to indicate there is a Solo selected, but it shows the same indication whether in SIP mode or normal Solo mode.