Change font, font size and font style for all elements in floating mode

Add this code to the Custom CSS field on the Style tab of your Audio Player widget’s settings:

.global-style, [class*="Playlist__Component"], [class*="FloatingBar__StyledPlaylist"], [class*="FloatingBar__Container"] {
    font-family: Calibri;
}
// Playlist items title
.global-style, [class*="PlaylistItem__Title"] {
    font-size: 15px!important;
    font-style: normal!important;
}
// Playlist item duration
.global-style, [class*="PlaylistItem__Duration"] {
    font-size: 15px!important;
    font-style: normal!important;
}
// Progress bar time start and end
.global-style, [class*="ProgressBar__TimeStart"], [class*="ProgressBar__TimeEnd"] {
    font-size: 12px!important;
    font-style: normal!important;
}