Machine keys are parts used to fasten components such as gears, pulleys, sprockets and couplings to rotating shafts. They are used for power transmission applications in machinery such as motors and gear reducers.
Square splines are used for smaller shafts and rectangular splines are used for shaft diameters over 170 mm (6.5 inches) or where mating hub wall thickness is a problem. Set screws are often supplied with keys to hold the counterparts in place.
In music, a major scale and a minor scale that have the same tonic are called parallel keys and are said to have a parallel relationship. The relative minor or tonic minor of a given major key is the minor key based on the same tonic; likewise, the relative major key has the same tonic as the minor key.
The definition of a relative key
Two keys are relative keys when they are based on the same note but differ in quality – a major and a minor . For example, C major and C minor are parallel keys.
Parallel keys have the same basic pitch but use different pitches in the scale. C major and C minor are parallel keys. They have the same root notes but use different pitches in the scales.
Hollow Saddle Key
This key is only useful for light transfers.
D minor is a D-based minor scale composed of the pitches D, E, F, G, A, B♭, and C. Its key is B flat. Its relative major is F major and its parallel major is D major.
Typically, songs can use two keys: the main key and then a modulation to a key a fifth apart. For example, starting a song in C major but having a section that goes to G major (G is the 5th chord in the key of C) and then comes back to C at the end.
The tonic chord is the first (or root) chord of the key. It sets the tonal center and creates resolution. The subdominant chord is the fourth chord in the key.
Enharmonic equivalent key signatures are keys with different names that contain the same pitches, such as B. C♯ major and D♭ major. Dorico follows the convention of transposing to keys with the same kind of accidentals as the previous key, except when the enharmonic equivalent key has fewer accidentals.
Parallel modulations alternate between major and minor keys that share the same root – for example, C major and C minor. This is often done over the dominant V chord common to both keys, which in this case would be G major.
What is the difference between relative keys and parallel keys? In music theory, relative scales and parallel scales are not the same. A relative minor scale uses the same notes as its cousin major scale; a relative minor scale has the same tonic (or first note of the scale) as its cognate major scale.
There are two options. First, you can count the number of sharps/flats in the major key signature and subtract three sharps/add three flats to get relative minor. Like E major ⇨ E minor goes from 4 sharps ⇨ 1 sharp. C major ⇨ C minor is also based on 0 sharps/quakes ⇨ 3 es.