Getting its name from the theoretical faster-than-light particle that puts physicists in a tizzy, Tachyon, a new music app from Jordan Rudess, shows that there is still plenty of room left for real innovation in the iPad music app space.
In addition to featuring many of the sounds and unique expression methods that Jordan has developed over the last few years, Tachyon allows for the seamless transition from one instrument to another, within the same note. The result is often subtle, but always effective. The accompanying particle effects that spin, swivel, rotate and morph as you play the notes and transition between instruments, provides pleasing visual feedback that goes beyond just entertaining graphics.
I've only played with Tachyon for a day or two, but I can already see a permanent place for it on my iPad.
App Store Link: Tachyon
Further Reading: Jordan Rudess