Well, well.

I think it's the other way around actually.

In most sessions I attend, there's always a big cry of "Hush!" whenever a singer performs or indicates they wish to do a song. Most musicians listen respectfully and don't chat nor do they go to the bar.

Singers are more likely to chat during "the tunes" as they just regard them as "background". Same as the punters.

I know some singers who deliberately attend tune sessions on their own as they know that the musicians there will kindly allow them to sing a few songs now and again at suitable breaks in between the "tunes". These singers are quite happy as they actually end up getting more songs in than they would in an actual singaround! Very crafty indeed!
:-))

I'm not criticising the above, of course, as long as he/she respects the fact that it is mainly an instrumental session. It's also quite nice to have your own resident singer.
;-))

"A feature of tune merchants' behaviour is to play several consecutive tunes."

These are called "sets".......

Anyway, most regular pubs sessions whether they be instrumental, song based, or a mixture of both usually have a fairly settled format where attendees know what to expect and generally know how to behave. In most situations, this works very well and there usually is enough respect.
Festival and other "one off" sessions are a different beast, of course.

Anyway, the point is that whatever Sandy Bell's was in Barbara's younger days, it is different now. It IS regarded as a music pub and *organised* as such. The main sessions are usually "led" by musicians who have their own "this is MY" nights and "lamentable" musicians aren't generally tolerated for too long in any case.

Of course, there are occasional deviations and an opportunity for a more spontaneous song or tune in between the more organised proceedings. So, there's still scope for some unpredictability and even a little conflict.