What is the lowest note a cello can play?
The lowest note a cello can play is a C2.
When all of the strings are tuned to the typical notes, the lowest note a cello can play is a C2, which is the open C string. This note has a frequency of 65.4 Hz.
It is possible to play lower notes by tuning the C string lower than the C2 intended. Though this is not commonly done, I have seen it requested before in one piece performed by my orchestra—though I cannot currently remember which piece that was.