2 For a “Psalm” is a song, not any kind of song, but a song to a psaltery. A psaltery is a kind of instrument of music, like the lyre and the harp, and such kinds of instruments, which were invented for music. He therefore who sings Psalms, not only sings with his voice, but with a certain instrument besides, which is called a psaltery, he accompanies his voice with his hands. Will you then sing a Psalm? Let not your voice alone sound the praises of God; but let your works also be in harmony with your voice....To please then the ear, sing with your voice; but with your heart be not silent, with your life be not still. Thou devisest no fraud in your heart: you sing a Psalm to God. When you eat and drinkest, sing a Psalm: not by intermingling sweet sounds suited to the ear, but by eating and drinking moderately, frugally, temperately: for thus says the Apostle, “whether you eat or drink, or whatever ye do, do all to the glory of God.”...If by immoderate voracity you exceed the due bounds of nature, and gluttest yourself in excess of wine, however great praises of God your tongue sound, yet your life blasphemes Him. After food and drink you lie down to sleep: in your bed neither commit any pollution, nor go beyond the license given by the law of God: let your marriage bed be kept chaste with your wife: and if you desire to beget children, yet let there not be unbridled sensuality of lust: in your bed give honour to your wife, for you are both members of Christ, both made by Him, both renewed by His Blood: so doing you praise God, nor will your praise be altogether silent. What, when sleep has come over you? Let not an evil conscience rouse you from rest: so does the innocence of your sleep praise God....
3. “Let praises be pleasant to our God.” How? If He be praised by our good lives. Hear that then praise will be pleasant to Him. In another place it is said, “Praise is not seemly in the mouth of a sinner.” If then in the mouth of a sinner praise is not seemly, neither is it pleasant, for that only is pleasant which is seemly....For praise may be pleasant to a man, when he hears one praising with neat and clever sentiments, and with a sweet voice; but “let praise be pleasant to our God,” whose ears are open not to the mouth, but to the heart; not to the tongue, but to the life of him that praises.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)