As recently as sixty years ago, there was very little in the way of literature for the double bass as a solo voice; it was barely even considered a particularly musical instrument. (And don’t get me started on double bass jokes. As the ancient sage Jimmy Durante once said, I got a million of ‘em.) But now, not only is there a substantial and growing body of work written for the double bass either alone or as the solo voice within an ensemble, there is an even greater and faster-growing set of recordings for double bass as a vehicle for adventurous solo improvisation. Two fine new recordings by Jakob Heinemann and Matt Nelson can claim to be part of this now-venerable tradition. Both albums are concise and to the point—Heinemann’s four tracks total 34 minutes, while Nelson’s five come to 23 minutes—in presenting each artist’s engagement with the instrument’s broad range of techniques and consequent palette of sounds. While both bassists make generous and almost exclusive use of techniques largely developed within the last several decades, each does so with a sensibility that’s quite specific and ultimately personal. Heinemann seems drawn to the instrument’s naturally dark woodiness of tone, something he brings out with a robust, heavily percussive touch using both hands and bow. He’s especially effective at combining bow strikes with a strong left-hand attack to create a dense polyphony of timbres. Like Heinemann, Nelson is attentive to subsuming pitch in unconventional sound colors, albeit in a way less oriented toward auto-counterpoint. He shows himself to be particularly adept at exploring the multiphonic possibilities inherent in subjecting heavy strings to varying pressures from bow and fingers; on two tracks he plays with the microtonal variations that arise from simultaneously sounding stopped and open strings.