These tanpura recordings are a good source for the drone ("sur" or "shruti"). This CD is an economical alternative to the shruti box. CDs are available in all keys, so it is important to SPECIFY THE PITCH when ordering. There are two tracks per CD, one is a Sa-Pa-Sa and the other is a Sa-Ma-Sa drone. Each track is 1/2 hour in length. Great for vocal or instrumental accompaniment & very popular as a meditation tool, ideal for yoga instructors & students!. Click on the Liston icon for a sound sample.