question: private AudioInputStream synthesizeVariant ( AudioFileFormat aft , Element domElement ) throws SynthesisException { int numberOfBackChannels = unitFileReader . getNumberOfUnits ( ) ; int backchannelNumber = 0 ; if ( domElement . hasAttribute ( "variant" ) ) { backchannelNumber = Integer . parseInt ( domElement . getAttribute ( "variant" ) ) ; } if ( backchannelNumber >= numberOfBackChannels ) { throw new IllegalArgumentException ( "This voice has " + numberOfBackChannels + " backchannels only. so it doesn't support unit number " + backchannelNumber ) ; } return synthesizeSelectedVocalization ( backchannelNumber , aft , domElement ) ; }
target:  Synthesize a "variant" vocalization