It’s so divey, you may feel the need to hold your breath at the Smog Cutter. Don’t. The shy or uninitiated find it less intimidating to try out their lungs here. There is no discernible stage: Singers are relegated to a darkened spot facing the backs of bar patrons, who glance over only occasionally. Song choices are mainly classic rock; one list had more Neil Diamond (43 tunes!) than Madonna (just 3). Tip the KJ (karaoke DJ) and you might move up on the wait list.