After 32 years of attending, visiting, and helming many studio recordings, I've come to recognize the impact that guests dropping by can have on a session. In Tape Op #73 I described my take on 'Etiquette for the Studio Visitor?' But, in reality, whether one should have visitors during any recording scenario (whether while home recording, on a remote session, or in a studio) is the actual question that should be asked. What a visitor dropping by will bring to the table can potentially be either helpful or disruptive. What is confusing is that many of the most common disruptive visitations are completely unintentional.
It's hard for anyone that has never been on the performers' side of the recording equation to understand the focus needed, the vulnerability present, and the amount of time some of the work takes. The more that the visitor is respectful of the attention needed for the project, the more positive their appearance will be. Remember, a friend or loved one quickly dropping off some (probably much needed) food or refreshments can be a real positive for everyone.
Some visitors can bring a needed uplift to a session. It might be a friend of the musicians, who is also a musician, that adores their music, and who is excited to hear the songs they love come to life. These people can provide a sort of "virtual audience" for the group. Sometimes a respected musician can be a boost to long day, and positive feedback on the work going on from a peer always feels great. As a bonus, impromptu 'guest spot' overdubs can sometimes shine a new light on a song's possibilities.
Family members can bring good or bad elements to a session, depending on the situation. Children can give a recording parent a nice boost, but as the studio can seem interminably boring to an outsider, keeping kids' visits brief is important.
Band managers and record label folks can be a mixed bag. Some bring the enthusiasm of a fan, and make everyone feel good about the project. Others may shine a more pragmatic light on the proceedings, and wonder why time (and money) is being spent on a particular song or part. Not exactly conducive for the most creative flow.