It’s named AltSoftSerial because it is a software-based serial library that is an alternative to the NewSoftSerial package.

Effects pedals: for some an object of overwhelming addiction, but for many, an opportunity to hack. Anyone who plays guitar (or buys presents for someone who does) knows of the infinite choice of p… ...

It's of course backwards compatible with existing Arduino add-ons, but sets itself apart with a new USB controller with lower latency and driver-free operation on Mac and Linux.