Another important idea about intonation is using the key signature and scale tones to “color” the pitches. For example, on a piano F# and G-flat are enharmonic, but strings can make a subtle difference between them. Also, the 3rd and 7th tone in Major keys “lean” or resolve to the next higher tone. Of course this is more appropriate in solo playing, but is also quite effective in small-group ensembles. I even teach this when my students are playing basic etudes. (Wolfahrt, Kayser, Kreutzer, Dont, Sevcik).