A = 415Hz.
The general standard tuning for baroque instruments is A = 415Hz, or a G# on the modern piano. Tuning for Renaissance music is often A = 440Hz, an A on the modern piano.
We're playing both Renaissance and Baroque music in this course, so I just had to make a choice.
HOWEVER! If you want to play at 440Hz, all is not lost! There is an excellent extension for Chrome that can shift pitch and slow videos down. You can find it at:
Transpose.video. Easy to install, easy to use.