Is the charmingly quirky “Drops of Water” a tune Buddy Holly might have recorded had he lived long enough to wrap his hands around inexpensive synthesizers? Milwaukee’s heartfelt songwriter and prolific recording artist Harvey Taylor travels across diverse territory on his latest album, Old Souls. Sometimes he sticks close to the guitar-harmonica folkie format. But he also branches out on the brooding eco-lament “Planet of Paradox,” given sonic depth by violinist Linda Binder. Similarly, the veterans lament “Soldiers” gains texture courtesy steel guitarist Tim Taylor. Another guest, slide guitarist Peter Roller, invests “Buddies” with the blues. Taylor choses his friends well.