Estimating tempo and measure lengths
I have some live performances recorded in the studio that I want to enhance with some bass lines and percussion. Since the performance is rubato, I will have to precisely adjust the tempo for each measure. I will need to have some method for calculating this. I can put the audio into a DAW and measure each measure of four beats in milliseconds, but how can I translate the milliseconds into the bpm tempo notation of Musescore, which measure bpm to the hundredth or thousandth of a second? Is there some formula that I could use with a calculator and get the most accurate result? The calculators available online are not all that precise. What's the formula?