You can be a greatest musician in the world but unless your instrument is in tune no one is going to book you more than once. However, if you spend half your set tuning up, no one will enjoy your performance either.
Audiences don’t mind if you have to tune up in the middle of your set, but they expect you to be in tune at the beginning of your set. I find it very difficult to re-tune a guitar while talking to an audience. I once broke a string on stage and then spent about 10 minutes tuning up only to discover than I had put a G string on the 4th string which meant that the guitar was impossible to tune up.
I do the following.
Tune up at home.
When I get to the gig I check my tuning again and leave the instrument outside its case to acclimatise the instrument to the heating of the room.
Then 5 minutes before I go on stage I check my tuning again.
I use an App rather than using one of those tuners that clip on to the head of a guitar – they are a lot more accurate. An App called Clear Tune is a good one around £2.99. I tune one guitar in standard tuning and the other in Open D. I don’t bother tuning my violin – tuning it just makes it sound worse!
I love playing in Open Tuning – but can stand re-tuning my guitar on stage. Much better to take 2 guitars. Check out Paul Brady’s video below – its a good example of Open Tuning.