Dear Sir, There is so a reason not to use a tuba, sitar or conga in Celtic music. Irish music has developed as a result of being played on certain instruments. While a number of instruments have been absorbed into the genre over the years (guitar, mandolin, cittern, harmonica,bones shakers, triangle etc. ), they have all been things that complimented without drastically changing the overall sound. A sitar, a tuba, and a conga all have types of music they are well suited to. As far as a recorder, as a purist, I'm not a big fan, but it can fit if played tastefully. But then, that's just my opinion. Slan, Rich