If I try to do stereo without having seewave installed, I should get a nice error.

[tlevine]

This is what I get now. I would like a nicer error that explains that I need seewave for stereo.

  sequence(list(piano$A2), list(beat.dynamics[1:100]), stereo = T)
Loading required package: seewave
  |======================================================================================================================================================| 100%
Warning message:
In library(package, lib.loc = lib.loc, character.only = TRUE, logical.return = TRUE,  :
  there is no package called ‘seewave’
Calls: sequence ... tryCatchList -> tryCatchOne -> doTryCatch -> library

[abelsonlive]

Am just adding a dependency to seewave and removing the stereo arg. All the built-in waves are stereo for now, so it shouldn't be a big issue. Eventually there should be a test for whether a wave is stereo.