הַשִּׁיר֙ יִֽהְיֶ֣ה לָכֶ֔ם כְּלֵ֖יל הִתְקַדֶּשׁ־חָ֑ג וְשִׂמְחַ֣ת לֵבָ֗ב כַּֽהוֹלֵךְ֙ בֶּֽחָלִ֔יל לָב֥וֹא בְהַר־יְהוָ֖ה אֶל־צ֥וּר יִשְׂרָאֵֽל׃
Ye shall have a song As in the night when a feast is hallowed; And gladness of heart, as when one goeth with the pipe To come into the mountain of the LORD, to the Rock of Israel.
Read kabbalistic (mystical) interpretation of Isaiah 30:29: and classical mystical sources.