Scales are what start on a stave in a tone which can go either forward or backwards. They’re done by tones & semi tones. They start off on the major scale with A sharp ending in G while the bass scale starts with G ending in A Sharp.
Intervals work as the main note acting as the root while the second is the tonic & the third note is the sub tonic. They’re numbered by 1-5 with perfect octaves, The octaves which are major go to minor as well.
The start out with F major with a number calculation. C uses one semi tone. Semitones make up a major third which go from A to G & are numbered individually. By counting up to the note of the scale you write out the number in an interval there’s always a tonic that becomes semitones making up the perfect interval in a song.
Modes are a 7 way system which consists of Ionian, Dorian, Phygrian, Lydian, Mixolydian, Aeolian, & Locrian. To help better remember this is a catchy acronym will work such as. Idiots Dig Playing Loud Music At the Library.
Modes are a series of tones & semi tones or whole or half steps. It all depends on which mode you’re using when you play & the difference is that they only use all white notes.
Stems are used to indicate the note you’re playing on the scale. They contain the note head which is on the bottom or sometimes the top. The stem points up or down at the middle line when the note is attached to it depending on where it is on the middle line.
The main difference is the upward notes are for high & higher voices such as soprano which is the high female singing voice while alto is for lower voices meaning the notes would be downward.