Male blackbirds (Turdus merula) were confronted with modified and unmodified playback copies of their own songs presented within the birds normal territories (Fig. 1). The vocal responses of the birds were recorded and correlated to the playback songs in respect to pattern specificity (song matching) and time specificity (distinct latencies). The following results were obtained: 1. The initial element of a song played a key role. If it was erased or masked by a pre-element the birds did not match the playback copies. In contrast erasure of the second element or the rest of the song following the second element did not affect song matching (Figs 3, 4). 2. The second element had an additional effect. The matching preference increased with a shortening of the pause between the first two elements, it decreased when the second element was substituted by an alien element (Figs 2, 3, 4). 3. A series of initial elements (identical or different element types) led to an inhibition of song matching. In contrast, copies including a doubling of the first two or three elements had a supernormal effect (Figs 4, 5). 4. Three types of song responses could be discriminated: in type I responses (latency: L = 0.1 s) the birds did not match the stimulus; in type II responses (L = 0.25-0.8 s) song matching was preferred; type III responses (L > 1 s) showed no time specificity towards onset of playback songs, but still a preference of song matching (Figs 6, 7). 5. In general, late matching responses (type III) were less preferred than rapid ones (type II) but the effects of different song modifications remained the same. 6. In type II responses, the temporal triggering of the reply and the recognition of the heard song class were not completely linked. In contrast to the neglectable influence of the third elements they were well able to trigger a reply (Fig. 9).