Chris Rutkowski, Composer/Pianist

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Step 2: Create a bar and beat timeline for the audio of each movement of the Concerto.

The Problem: Audio files in a DAW are displayed as waveforms in a timeline, which shows where audio events happen in time. If the audio is recorded without a metronomic click track, then there is no direct correlation between a given downbeat in the audio and the bar/beat timeline used for sequencing MIDI instruments. Thus, in order to add MIDI instruments to the Concerto audio, (to correct dynamic imbalances in the recording) a bar/beat timeline must be created and correlated with events in the audio.

The solution: Logic has a function called “beat mapping”. What it does is adjust particular beat positions in the bar to events in the audio by calculating small changes in the tempo-e. g., the basic performed tempo of the third movement was 105 beats/minute, so if a bar or beat is rushed, Logic will insert a change of tempo for that area when a particular beat is linked to a particular rushed note.

How does it do this? First, I had to recreate the entire metric structure of the score in the Logic file, i.e. changes in time signatures where they occur. Beat mapping displays the audio waveforms under the bar/beat map. The next step is where the magic happens-Logic analyses the waveform for “transients”, which are essentially spikes in volume at the attack points of given notes. Referring to the score, one can draw in a link between a given beat and a particular transient, thus giving Logic two points in time with which to calculate a change in tempo.

Voila! There is now a grid imposed on the audio which can be used by the sequencer to trigger virtual instruments. The first such instrument I used was a trombone to beef up the bass in the 3rd movement-but more about that in the next post.

One last preliminary: I had to get score information on what notes to play into Logic’s sequencer from the score. This was not as easy as I had hoped, but victory was had at last. Finale will convert the score information into a Standard MIDI File of note on/off information, which can be read by the sequencer, which, in turn, tells the synthesizer when to play a given note and how long. Unfortunately, when I made a SMF of the trombone part, it included a lot of other instrument information, and caused Logic to create many more than the one track needed. The solution was provided through a long chat with Finale tech support (not toll-free, but that’s what Skype is for!). Apparently, when the part was extracted from the score, it kept the instrument list (for Finale’s own playback) from the score. I simply had to delete all the extra instruments in the Finale file before saving it as a SMF and importing it into in Logic. The moral: everything has to be massaged….