I think personally it is mainly diet and weights that contribute to muscle growth. Is sleep that important of a factor too? Are there substitutes for sleep, like meditation, for example?
100%, I've been training for about 5 years now and there was one spell were due to work I was living off about 4-6 hours sleep a night for a month. I still exercised and dieting like i normally would but I actually loss muscle strength. Sleep is were all the hard work pays off, its the chance for your body grow and recover. Without the proper recovery you wont see any benefits!
You grow when you sleep. When I was competing I would take simplysleep to make sure that I got 9 - 10 hours of sleep a day. IMHO, sleep is only second to eating in terms of growing muscle. Ironically lifting weights is a distant 3rd, especially in terms of willpower. Anyone can lift weights. Few can get enough sleep. Fewer can stick to a diet. As much as our minds won't allow it, our bodies love a consistent routine. Eat every 2 hours, work out in a routine as scheduled (same time), and go to bed at the same time and wake at the same time - and preferably not by an alarm clock. Your body doesn't really care that it's the weekend, your mind does.