Lewis,
Basically when going from low to high, you can:
- Let go into a weak head voice or falsetto: "As soon as I go into head voice I sound weak and quiet compared to my chest voice."
- Push chest voice and strain: "I've sung for years but had to avoid songs like that because my chest voice range won't get those high notes. "
- Gradually move from chest voice to head voice so that you don't hear any sudden shift in quality and you think the singer has a 2-3 octave chest voice range.
Nick