I'm scoring a piece for SATB choir and there is a moment that I want a melody sung in unison/octaves by the whole choir. The melody spans an octave. I first conceived of the melody in A minor, where its range spans from E to E. This would be perfectly fine for soprano and tenor, but sits too high for alto and bass. But if I transpose the melody down much lower, the sopranos and tenors begin to bottom out their ranges. I know that it will not be perfect.
What range for a one-octave melody is likely to be most successful and least uncomfortable for the singers in a standard SATB choir? Are there examples in the literature that use choral unison/octave over a range this large?
I would rather not ask any voice part to change octave halfway through.
I'm thinking spanning from C to C is the most attractive option. That notion is supported by this question (link), which mentions the same range but for amateur singers instead of trained musicians. If it matters for this question, the choir is auditioned, professional ensemble.