I am using a UNO R3 with an Adafruit Musicmaker shield. I would like connect an NRF24L01 transciever to the UNO and receive commands to play certain sound files through the Musicmaker shield. Pin 11 is needed for the Musicmaker shield and the NRF24L01. I am concerned that there might be some kind of conflict with both using this pin. Am I correct that there might be a conflict? Is there a way to reassign the MOSI to another pin so that I can connect the NRF24L01 MOSI to that pin? Can I use the SPI MOSI for the Musicmaker shield and and pin 11 for the other? How do I go about doing this?
MOSI is part of the SPI bus, which supports multiple devices. As long as that musicmaker is using SPI itself, you can share this pin. You can not just assign it to another pin, it's in hardware.
Each SPI device must have their own CS aka SS pin.