I am trying to align a stereo track click track in a DAW with the stereo track of a rap song. I wasn't sure if I should start at the very beginning of the song (00:00:00) or wait till the first beat in the song ( where their is first change on the graphs for Amperage or Pitch ) , or on the first beat of the lyrics? Wouldn't starting at the beginning not work if there is silence that isn't part of the count since the first beat of the first line hasn't started? Finding where the beat is for the first lyrics or any random point is hard because it's hard to precisely find where that exact point is? I mean that there is waves on the aptitude or pitch graph before and any random beat that doesn't have silence before it? I am going through the reasons why I think finding the very first beat would be easy and now asking you if this is right given that their is a constant in the graph before the first beat. Am I right on the approach to most precise accuracy?
If your song is at 83bpm then seeing your metronome at 83bpm will mean you have the right tempo. What I think your question is getting at is starting correctly on the beat, correct?
If so, the usual process is to have your metronome started first so you can come in correctly, for example you could let it run for for bars and then jump inti the fifth bar.
If your problem is that you have a recorded instrumental track and it doesn't have a beat so your metronome is running separately then you either need to define a start signal on your track to cue up the metronome or just record a click track with your instrumental track. This is what various electronic bands do if they have a live drummer:
Most DAWs will let you record your tracks and run a click track, so you can send your audio to house pa and monitors and just send your click track to your own monitor. This will require a system with enough tracks so you can separate them out.
The underlying question, dug up from comments:
Use Audacity's time shift tool to move the click track to begin on the first identifiable beat in the song, past its intro.
Make a not of the time shift that is required: how many seconds and milliseconds.
Then, if the song really has an accurate tempo throughout, and the click track nails the exact tempo, it should stay in sync through the rest of the song.
If not, generate a faster or slower clicktrack, and time-shift it to the same starting position as before. You probably do not have to use the time shift tool any more because Audacity's dialog for generating a click track lets you enter an offset (up to 30 seconds).
If the click track is slow or fast, find the point in the song where the click track falls behind or races ahead by a full beat. Make a note of the time difference, in seconds, between that point and the first beat. Call that T. The reciprocal of T, or 1/T, is the error in your click track.
Example: The click track falls behind by one beat in about 85 seconds of song (measuring from the first beat). Thus the error is 1/85 or about 0.011765 beats per second. Multiply by 60 to convert to beats per minute: 0.706. So, instead of 83 beats per second, you need about 83.706. (We add the error, since the click track is slow and falling behind.) So now, blow away the click track and generate a new one at 83.706, remembering to offset it to start on the song's first beat using the offset time noted earlier. Then check it again: if the click track is still ahead or behind, repeat the calculation again to figure out more offset to add or subtract; the error should be smaller this time, and hopefully will nail the tempo right to the end.
Of course, if the song has a time-varying tempo (it's one of the rare rap songs produced with a real drummer) you're out of luck with this approach.
If the track and the metronome go out of sync, then either the metronome or the track is not exactly 83bpm.
My money's on it being the track. Digital metronomes are very accurate.