Implied Metric Modulation
One of my favourite concepts is implied metric modulation – making it sound as if the tempo has changed when it fact you're just superimposing a new tempo over the existing one. You hear a lot of jazz and prog rock drummers use this but why should they have all the fun?
For this lesson, we're going to use a walking bass line over a 12 bar blues in Bb. There's a lot of stuff crammed in here and I wouldn't recommend using all these concepts in the space of 12 bars but for the sake of demonstrating the idea:
Let's have a look what's happening here. The first modulation happens in bars 2-4 where we play a note every three eighth notes giving the illusion of the tempo slowing down and then speeding back up in bar 5. The next “gear change” occurs in bars 7 and 8. Here we play quarter note triplets (3 notes in the space of 2 quarter notes) but play them in groups of 4 rather than 3 giving the impression that the tempo has increased (the notes imply the chord changes Bb7-Ab7-G7). The final, and craziest, modulation is saved for the last two bars. This is similar to bars 7 & 8 but this time it's 8th note triplets in groups of 4 implying a run of II-V changes – Dm7-G7-C#m7-F#7-Cm7-F7 at a much faster tempo.
The first soundfile demonstrates how this can sound if the drummer plays the modulations with you, the second file is the same bass track over a click track so you can hear the “new” tempo over the original one. The trick with this stuff is to always hear the original tempo in your head so you know how to come back, otherwise you could be heading for a train wreck if the rest of the band jumps on your new tempo and no one can work out where the original tempo is!