I am not sure where this track is leading, but I found a few errors in the one just past.
1. Electronic tuners are not tempered, so if you tune to A=440, that being the A below "middle" C, and play the A´s in the other octives, gowing down you will get 220, 110, 55, etc, and up you will get 880, 1760, etc. On a tempered keyboard, 110 and 1760 will not sound right with a piano, which is what "a well tempered clavier" is all about.
2. While I agree that a fiddler needs to be able to do relative tuning, what makes you think that the first string is correct without a tuner? If the band takes its pitch from a tuner, the electronic keyboards are then tuned by turning the dial, the winds (except where already mentioned in the upper registers), will then be in tune. The strings, however, will now have only one string on pitch, which means that a good fiddler should do both, tune to the fifth, then check with the tuner. If they do not match, there are two possible errors, he has misheard his fifth, or his initial string is out of tune (which happens as easily as changing the room temperature or brushing the peg when tuning the other string.