I've never experienced the need to fill in time. Gaps in performance are not usually enjoyed by the audience. Always thought it unprofessional. However, I've been watching Vulfpeck concerts recently and they do it all the time. Have a look.Thanks for the suggestions. Sorry if there was any misunderstanding but my question wasn’t only about that one song or C tuning, it was more asking for an “everyday tool”, something that you can use at a given time to fill up time, regardless of the reasons why.