Identifying birds by their sounds is difficult though a crucial piece to become a good birder. Alison Kondler has written a non-published bird sound field guide using her unique mnemonic teachings. Her dream is to convert this book into a mobile app with video, images, bird sounds, and mnemonics. Having these teaching in the field would help to create memory bridges instantaneously. No need to go home after the fact, open a book and listen to a CD or online sounds, because by then, the bird's sound will be forgotten.
If you need help identifying birds by their calls and songs, please support this amazing venture.