nextcloud-breeze-dark/core/css/apps/_music.scss

.app-music #app-navigation {

    .app-navigation-separator {
        border-bottom-color: $decoration-normal;
    }
}

.app-music #app-content {

    #emptycontent, .emptycontent {
        background-color: $background-normal;
    }

    #toScan:hover * {
        color: $foreground-active;
    }

    .alphabet-navigation a {
        opacity: 0.2;

        &.available {
            opacity: 0.7;

            &:hover {
                opacity: 1;
            }
        }
    }

    #controls {
        margin-top: 1px;

        .progress, .seek-bar {
            background-color: $background-dark;
        }

        .buffer-bar {
            opacity: 1;
            background-color: $background-active-hover;
        }

        .play-bar {
            background-color: $background-active;
        }
    }

    #app-sidebar {

        .close, #follow-playback {
            background-color: unset;
        }
    }

    #music-user .warning a {
        color: $foreground-link !important;
    }
}

#music-controls {
    background-color: $background-normal;

    #albumart {
        border: none;
    }

    .seek-bar {
        background-color: $background-dark;
    }

    .buffer-bar {
        opacity: 1;
        background-color: $background-active-hover;
    }

    .play-bar {
        background-color: $background-active;
    }
}