
Peach liqueur is a sweetened liqueur made by infusing peaches (and sometimes their kernels) into a neutral spirit.
Everything on the stone-fruit shelf lands near it on sweetness; what separates the bottles is whether the fruit was steeped or flavored in. That is the half to judge before you pour, because measure alone will not fix it.
Flavoring and sugar on a neutral base, simpler and less natural: it pours one for one, and the flavor comes out candied rather than fruity.
The neighboring stone fruit at the same sweetness, poured in the same measure; the drink holds together and its fruit turns honeyed rather than juicy.
Peach liqueur fades early even by the standards of fruit liqueurs — the aroma is the volatile part and the color goes with it. Closed, cool and out of the light, and treat an open bottle as a matter of months.