public void stop(String sourcename) {
		if (sourcename == null || sourcename.equals("")) {
			errorMessage("Sourcename not specified in method 'stop'");
			return;
		}
		if (midiSourcename(sourcename)) {
			midiChannel.stop();
		} else {
			Source mySource = sourceMap.get(sourcename);
			if (mySource != null)
				mySource.stop();
		}
	}