Logic 9 Beat Mapping of MP3s for BPM Value
I have been using Logic9 at college to analyse the chord structures of some Jamtracks, by placing markers at each key change, then playing a bass note on the MIDI keys to verify what key that bar/beat is in. This is a very educational process for someone with no formal music training as you get the benefit of insight of the compositional skills of the talented guys at Jamtracks who create these improvisational tools, as well as some keyboard lessons when trying to find the particular chord(s) that may work for that section.
As they are widely based on standard and classic artists chord structures and genres it gives you a faster track into learning composition structure, and to help solo over as many different music styles as you are interested in, as it is helpful to know what the chord structure is mentally rather than knowing a track just by ear, but not knowing what to play over it by ear yet. These are two different key skills so it is best to know and be able to use both for obvious reasons. Thinking about chord structures mentally while playing is something alien and very new to me, so not easy for me to learn.
But, if you lose your way sonically in a solo, you can pick back up visually on the fret board if you know what the next chord is structurally. Musicians who have had formal sight reading training are going to mentally visualise the process of improvisation differently than players that learned “by ear” alone.
How the improvisational process works from person to person is an interesting area to think about, as it is not something I have had many conversations about with other musicians oddly enough. I have chatted about the “meditative” state you can enter when playing/improvising for hours, which can be a pleasant mental space to be. This is partly why musos have to “warm up” for a while before they are in the right space to play well or capture a mood or unique solo.
No doubt it is very different mental process for wind players compared to strings players also due to our natural breathing actions when expressing language, so blowing a note has a whole set of different dynamics than plucking a note.
Once the root note is identified, it is enough for me at an early stage to identify the 3rd and 7th notes as major or minor.
I then have a chord chart that a competent formally trained and experienced keys players like JB can follow (and correct usually!) to either solo over, or help me with more interesting chords that can be used for that beat/bar. In Logic, the score editor can then print out in dots notation if required, once the MIDI notes are entered. Below is my current chart for Cuban Heel.
I have had issues with using the Tempo detect function (Audio menu drop list) in Logic 9 trying to find the BPM of some MP3s, as twice this tool could not analyse a given MP3 at all, or just gave a wrong value for the BPM.
I investigated further and found the Beat Mapping function. This worked very well though it is a bit more involved. To be fair to the basic Detect Tempo function in the Audio drop menu, it seems that the MP3 of the Happy As Larry Jamtrack (below) seems recorded without a click track, so drifted in and out of time slightly (naturally!), and also had different and changing tempos for the start and end of the whole track, which is possibly why the Tempo detect function gave a seemingly incorrect reading of 108 BPM – possibly an average for the whole track? More research required there.
Here is a set of screenshots of some operations required to find the BPM accurately, map the beats, then align the beats with the correct bar/beat markers for that songs BPM and set the project tempo to that BPM from the default 120 BPM of a New Project:
Above – drop the MP3 into a new audio track, then pull down the bottom left corner of the track name box to widen the track view.
Above – stretch the view to a high resolution then use the scissor tool (Esc menu) and cut close to the first count in beat, remove the cut section.
Above – drag the track back to the start.
Above – shrink the view back to full track overview to see any obvious tempo changes for info. With this beat marker method, the whole track can be marked on a beat by beat or note basis so individual sections don’t have to be analysed separately seen as later below.
First, expand the Global Tracks tree in the top left of the Track window, then expand the Tempo tree, and RClick the area around the Tempo box to show another menu where the Beat Mapping option can be unhidden:
Click the Beat Mapping button to analyse the track:
Once done, there is the option button to decide the Tempo resolution over section lengths – ¼ note values worked well to give a sensible overall BPM.
The MP3 waveform can then be snapped to a beat.
Each beat then has a tempo decoded for it which is shown changing per beat on the blue automation line along with white beat markers along the waveform:
The BPM counter in the Transport will now change for this variable BPM track, with each beat value when played.
Once the mapping has been done the chord chart can be mapped, labelled and colourised for easy visual reading:
If the chart is to be read in real time when recording say, record with the Piano Roll window showing also, as it gives a better time line reading resolution view experience to see what chord is coming next.