This recording has helped thousands of folks become martin landlords when played loudly from outdoor speakers or a boombox. Any martin within hearing range will be lured in to investigate. The CD is 74 minutes and also comes with instructions. Especially effective when used along with decoys. The recording was produced at the Library of Natural Sounds of the Cornell Laboratory of Ornithology. Playing this recording for one or two hours before dawn is ideal, but it can also be played any time of day during the two to four month period when migrating martins are arriving. With the purchase of this item, you will receive a three month subscription to the Purple Martin Conservation Association, limited to one free subscription per household. Purple Martin Market Place offers high-quality items for martin enthusiasts. Buy with confidence knowing that we have directed the development of much of the merchandise and what we offer has been approved by the Purple Martin Conservation Association. Profits generated support the PMCA's conservation, education, and research programs.