Song learning in birds is a process of memorising a song model and subsequently trying to match its own vocal output with the memory formed. Thereby, each syllable including the silent interval preceding it are copied as a single unit (Williams and Staples 1992). Zebra finch song consists of a chain of syllables repeated several times making up a bout, and is preceded by introductory notes (Sossinka and Boehner 1980). Birds raised with no access to adult song models develop a song (untutored song) that differs from normal song (Williams 1993), but is initiated by a string of introductory notes (Price 1979). Therefore, the question arises whether the introductory note is genetically determined. To answer this question we recorded and quantified a total of 376 introductory notes of song from normal (n=8) and untutored birds (n=6). The duration of the introductory note (syllable length), as well as the preceding silent interval (syllable period length) and the frequency of energetic maximum were analysed. Syllable length differs slightly between normal (51+/-2 msec) and untutored birds (67+/-7; p=0.053). Syllable period length, however, was significantly longer in untutored song (183+/-13 vs. 122+/-14 msec, p=0.02). Therefore, we conclude, that the length of an introductory note is genetically fixed, while introductory note period length is a learned feature of song (supported by the Deutsche Forschungsgemeinschaft SFB 515 to B.E. N.-B.).