This demos how to use an arbitrary .wav file as the instrument in java.sound.midi Synthesizer.

SampleInstrument.scala

import javax.sound.midi._
import com.sun.media.sound.AudioFileSoundbankReader

object SampleInstrument extends App {

  // AudioFileSoundbankReader allows an individual .wav file to be interpreted as an instrument
  val sbr = new AudioFileSoundbankReader();       
  val sb =
    sbr.getSoundbank(new java.io.File("./resources/bassoon-g4.wav"))
    //sbr.getSoundbank(new java.io.File("./resources/sin256.wav"))
    
  val synth: Synthesizer = MidiSystem.getSynthesizer()
  
  synth.open()
  synth.loadInstrument(sb.getInstruments()(0))    //> res1: Boolean = true
  
  val channels: Array[MidiChannel] = synth.getChannels()
  
  channels(0).noteOn(50,60) // idk what these numbers do :/
  Thread.sleep(1000) // hold the not for a sec
  channels(0).noteOff(50)
  
  synth.close()
}