Many questions arise when considering how to climb the mountain of playing Bach's Cello Suites on electric bass. One of the key questions is the question of keys. The original keys for the six suites are G major, D minor, C major, E♭ major, C minor, and D major respectively. Other than the fourth suite, these keys lie naturally on the cello, which is tuned in fifths and whose open strings (from lowest to highest) are C-G-D-A. Thus five of the six suites can benefit from the harmonic resonance of open strings, which is especially important when playing the suites on a Baroque cello. (Those who play in a more Romantic style don't like the notes of the open strings because you can't generate the requisite vibrato.)
The bass, whether double bass or electric bass, is by contrast almost always tuned in fourths: E-A-D-G. As a result, the two suites in C and the suite in G no longer lie naturally on the instrument. Many bassists work around the problem by transposing to new keys (e.g., transposing all the suites down a fourth as Mark of Bach2Bass.com has done or using some other heuristic for new keys as Paolo Rizzi did in his sheet music edition for Recordi).
But notice that phrase "almost always" in the preceding paragraph. Another approach is to tune the bass in fifths: C-G-D-A, just like the cello but one octave lower. Now you can play all the suites in their original keys and take advantage of those open strings. The biggest downside is that you have to retrain your fingers (all that muscle memory of how to navigate the fingerboard in fourths!). Jazz double bassist Red Mitchell started doing this back in the 1960s; following Mitchell's lead, classical double bassist Joel Quarrington has made a compelling case for tuning in fifths and has influenced a number of bassists to follow suit, especially in his native Canada.
I've been experimenting with fifths tuning and to my mind (and ears) it makes a lot of sense. Finger retraining is in progress! Unfortunately there are some instrumental challenges involved, which I'll cover in the next installment.
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