The Revised(5) Report on the Algorithmic Language Scheme (R5RS) is the canonical definition of Scheme, and it's a surprisingly nice read. The author learned Scheme from this document together with the Guile documentation. Debian GNU/Linux users can install the r5rs package so you can access it via info r5rs.
The Internet Scheme Repository contains an extensive Scheme bibliography, as well as papers, programs, implementations, and other material related to Scheme. (FIXME: Is this true?)
info guile.info is a complete reference on programming in Guile Scheme. info guile-tut.info is a gentle, although outdated, primer for programming with Guile, although it talks more about the C interface than the Scheme interface.
Documentation for GOOPS, the object model used by soundscrape, can be found in info goops.
man readlineThe manual page for the library function readline. Useful as a keybinding reference.
info guile.infoIf you look under guile's info page, then go to "Readline Support", then to "Readline Options", you can read about how to configure the number of previous commands to remember, among other things.