📒 completely flat and even, without any rough areas or holes
📒 without any solid pieces
📒 happening or continuing without any problems
📒 even and regular, without sudden stops and starts
📒 very polite and pleasant, but in a way that is often not very sincere
📒 pleasant and not bitter
📒 nice to hear, and without any rough or unpleasant sounds
📒 to be simple and free from trouble