I sing in a choir that performs a lot of music containing very close, tone-cluster type harmonies. We stand mixed rather than in sections, so it's especially challenging to find my pitch and maintain it. Worse, I'm an "inner voice" (tenor).
In rehearsal, I can cup one of my ears to hear myself better, but that looks pretty bad in performance.
1. What at-home exercises will improve my skill in this area?
2. How can I help myself within the ensemble?
I am comfortable hearing and singing intervals, fixed and moveable do, and singing common-practice music. I'm looking for techniques to address non-tonal music and finding/holding pitch within clusters/heavy dissonances.
A couple examples of the kind of music I'm/we're singing, timed to illustrative parts.
"...a riveder le stelle", by Ingvar Lidholm
Figure humaine, "VII: La menace sous le ciel rouge", by Francis Poulenc