There is no particular theme for this collection of solos; they're simply solos Ace wrote for bass clarinet. Some of them are re-workings of songs he's previously written, and some of them are new inventions from his imagination. They've been written with the low-C extension in mind as this becomes a more and more popular choice for bass clarinetists. His intention (if there was one) was to show off the lower range of the instrument, so if you have the low-C extension, now's your opportunity to utilize it.