Ever heard a sea eagle, pine marten, adder or red squirrel?
The sounds of the UK's rarest species of birds, mammals, insects and frogs have been put on to a compact disc.
Vanishing Wildlife is compiled by the British Library, which says it is a "call for action" to aid animals facing extinction from shrinking habitats.
Among the 31 species featured is the last recording of a group of pool frogs before they disappeared from the UK.
But there are some good news stories too. Bittern numbers fell to single figures but have since recovered.
Richard Ranft, of the British Library Sound Archive, says the CD works on several levels.
"One is a call to attention to these species in imminent danger of disappearing from our countryside or those that were on the brink of extinction but have been helped by conservation measures and still need help to secure their future.
"But they are also extraordinary sounds to listen to, listen and escape to various corners of the British Isles.
"The woodlark has a most exquisite song and people think of frogs as not having a pleasant sound but these are probably the last few individuals 20 years ago, making quite a lovely musical sound."
Mr Ranft said the threats to these 31 species varied but it was sometimes due to deliberate persecution, in the case of adders or birds of prey.
Hen harriers prey on grouse and are targeted by gamekeepers
Inadvertent accidents were also a factor, like deer fencing which birds collided with.
But a key reason was the loss of habitats, because they were destroyed or because they receded due to global warming.
In many cases these sounds are the only way to locate these animals, said Mr Ranft, so anyone hearing them in the wild should contact their local conservation group. Other than that, supporting such groups is the best way to help.
For years the British Library has been collecting sounds from a network of sound recorders, who have to endure many hours of waiting in the wild.
"These animals are very wary of man. The fact they are endangered may be due to persecution which would make them even more wary, so to get them singing and playing under natural conditions is quite a feat."
And Mr Ranft's favourite sound? The capercaillie, which he likens to the sound of wine being slowly poured from a bottle.
THE SIX SOUNDS REVEALED (IN ORDER)
The noctule bat has been hit by a loss of habitat and food. It likes to roost in hollows and trees which are disappearing and it eats pest insects - to the benefit of farmers - which are also less in number. The sound here has been through a bat detector because it is sonar.
The capercaillie was reintroduced in Scotland following extinction in the 18th Century but has since become threatened again. Its population is rapidly declining, falling from 20,000 20 years ago to only 900 birds today.
The field cricket needs a wetland habitat but this is drying out. It sings at night and the trilling sound carries a long way. It has become extremely rare although attempts to reintroduce them in Sussex has met with some success.
Numbers of woodlark have fallen dramatically. It can be found in southern Britain particularly on heathland but this habitat has become very scarce because it is often reclaimed for other purposes.
Otter numbers are up again
Sightings of otters have increased by 527% since their decline in the 1950s and 70s when numbers were seriously threatened by water pollution and wetland drainage.
Pool frogs have been re-colonised
Twelve years ago, the Norfolk pool frogs became extinct but it was re-colonised with introduced animals from Sweden in late 2005. Excavations of Anglo-Saxon sites revealed 1,000-year-old pool frog bones genetically similar to those found in Scandinavia, so scientists believe some developed in eastern England and went to Scandinavia up to 8,500 years ago.