These thoughts are more musing about technique becoming behavior. I am always amazed at how many singers - music theatre and opera - really don't know the difference between warming up the voice, and building the voice.
I always use going to the gym as a point of reference. Singing is athletic, therefore many of the athletic activities we do can relate.
When going to the gym, we SHOULD (and how often haven't we?!) warm the body up first before doing anything too strenuous - ease into the cardio and certainly stretch the muscles before building and breaking down and building with weights. Why would it be any different with the voice? The voice is about muscle development and balance and coordination. It is about stamina and breath and about vibration.
So - warming up in order to SING something is not building the instrument. Warming up the body and the voice should happen regardless of whether you are going to sing through a song or aria or work on technical balance or building balance. Warming up vocally should begin with the entire body's permission - engaging the full support and elasticity and stretch so the breath becomes tangible the vibration of one's sound is moving and flexible. This is NOT technique. Breathing and supporting as a singer is unlike anything else we do in our day to day. We must discover that athleticism in how we warm up both body and sound and breath.
If we choose to build the voice - again this is NOT singing. Building exercises to develop the vocal muscles and therefore the full capacity of the voice as behavior take time, focus and an understanding of WHY you are doing what you are doing and for what reason. The voice needs to discover itself in order to function fully and healthily.
Vocal building, I believe, happens in three main stages - the discovery of the entire instrument in its neutral position (not influenced by style); The development of articulation power - eg. legato, staccato, fioritura, messa di voce etc; The development of stylistic technical prowess - eg. operatic voices need certain physicality, music theatre singers need other physicality. Opera singers are not going to sing Mozart like they sing Puccini; Music Theatre singers are not going to use "belt" in the same way as they would a more "legit" sound.
These are 3 HUGE stages and can be worked on and discovered and maintained and worked on again to find further levels of development within each stage.
Ultimately, I believe, the neutral position of the voice - finding the core of the sound and balance within the body - is primary to EVERYTHING a singer does. The vocal building exercises and vocal maintenance exercising are about FUNCTION of the instrument. This behavior does not need to take on hours and hours of one's time - but rather focused, committed grounding to HOW and WHY to allow that instrument to develop fully.
The voice cannot truly learn to SING until these balances are discovered consciously. We need to know WHY we do what we do, and HOW to do them within the balances of our physicality.
Keep exploring HOW your body and breath and vibration need to warm up. Keep exploring HOW your voice functions and HOW to develop it to its fullest potential. Find your best self through your voice.
It is only the beginning. Find out how your voice behaves - and then ingrain a behavior that allows it function at optimum.
We can't do this ourselves! We ALL need a second set of ears, no matter what stage we are at in our development. Find a teacher you can trust, that will guide you allow this part of the journey.
Remember, warming up is NOT vocal building; it is NOT technique. You cannot "practice" in the car! Here is a perfect example of no multi-tasking!!!! FOCUS ON YOUR VOICE!!!! Don't think you can truly do it justice while you try to do anything else. Give that unique instrument the attention it deserves and the time it requires.
Your voice deserves it. YOU deserve it.