The present invention primarily relates to the use of an aldehyde, substituted in alpha position by an alkyl residue, of the formula ##STR00001## having (I) a total of 13 C atoms, wherein R means an unbranched alkyl residue having 6, 7, 8 or 9 C atoms and R' means an unbranched alkyl residue having 2, 3, 4 or 5 C atoms, or (II) a total of 15 C atoms, wherein R means an unbranched alkyl residue having 8, 9, 10 or 11 C atoms and R' means an unbranched alkyl residue having 2, 3, 4 or 5 C atoms, or a blend comprising or consisting of two, three or more such aldehydes of type (I) and/or (II), as an odoriferous or aroma substance.