▁is ▁in ▁a ▁lower ▁pitch ▁( typ ically ▁F ); ▁the ▁bass et ▁horn ▁pred ates , ▁and ▁und ou bt edly ▁inspired , ▁the ▁bass et ▁clar inet . ▁ ▁The ▁bass et ▁clar inet ▁was ▁most ▁not ably ▁associated ▁with ▁the ▁clar inet ▁virt u oso ▁Anton ▁Stad ler ▁( 1 7 5 3 – 1 8 1 2 ), ▁a ▁contemporary ▁and ▁good ▁friend ▁of ▁Moz art . ▁Moz art ▁wrote ▁his ▁Clar inet ▁Quint et ▁in ▁A ▁major , ▁K . 5 8 1 ▁and ▁Clar inet ▁Con cer to ▁in ▁A ▁Major , ▁K . 6 2 2 ▁for ▁this ▁instrument ; ▁the ▁con cer to ▁is ▁partly ▁based ▁on ▁an ▁earlier ▁fragment ▁of ▁a ▁Con cer to ▁for ▁Bass et ▁Horn ▁in ▁G , ▁K . 5 8 4 b . ▁ ▁There ▁is ▁an ▁aria ▁in ▁Act ▁I ▁of ▁Moz art ' s ▁last ▁opera , ▁La ▁cle men za ▁di ▁T ito ▁( the ▁mez zo - s op rano ▁S esto ▁s ings ▁Part o , ▁ma ▁tu ▁ben ▁m io ), ▁which ▁features ▁a ▁bass et ▁clar inet ▁ob bl ig ato . ▁ ▁As ▁noted ▁above , ▁a ▁bass et ▁clar inet ▁is ▁an ▁A ▁or ▁B ▁clar inet ▁with ▁an ▁extension ▁of ▁a ▁major ▁third ▁or ▁perfect ▁fourth ▁down . ▁The ▁deep ▁sound ▁of ▁the ▁additional ▁t ones ▁is ▁in ▁fact ▁rem in is cent ▁of ▁a ▁bass et ▁horn ▁in ▁F ▁or ▁G . ▁In ▁the ▁case ▁of ▁historical ▁instruments