Here is a sample of one of my lessons, with kind permission from my student Peter.
Peter is 64 years old and has been learning to sing for two years. The lesson was conducted at 9am-10am, meaning no warm up was conducted prior to the lesson* (and I was about 5 minutes out of my pyjamas). If you listen to the whole thing - or just jump to a few minutes from the end, depending on your attention-span - you will clearly hear the progression of his voice as it limbers up under my guidance.
*although we did some light warm-ups prior to the start of the recording.