[S]This was probably known already oops.[/S]
The tuner can 100% your solo while using playing instrument[S], and when in a jam only the person who is starting the jam needs it to get 100% accuracy.[/S]
Edit: [S]So far, the test has been done with only me and another friend, and out of 3 tries all were successes. I need to use more people when I get home to truly test 100% for sure.[/S]
Edit 3:Eh...doesn't work as I had anticipated. Good thing I did more tests but still...disappointing. After a painstaking 1 hour, I got some mules to just the bare minimum to get Jam Session. Then, I played the jam and...well...the results were not what I expected. The mules were not able to play the music at all haha...I guess this may possibly mean that it won't work with just one sadly. I apologize for the mis-information of this part.
Edit 2: For those who are hoping that it guarantees 100% haunting BFOs, nope. (Only added this since a friend was hoping it did).