How many fingers does bad pianist need?
Perl 6, 27 bytes

{+minmax [\+] @_ Z&lt;=&gt;0,|@_}

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Explanation
@_ Z&lt;=&gt;0,|@_ uses the zip metaoperator (Z) with the compare operator (&lt;=&gt;) to zip the list with itself offset by 1 and return the result of the comparison., e.g. [43, 48, 48, 48, 52, 50, 48, 50] -&gt; (More More Same Same More Less Less More)
[\+] Reduces the list by summing over it (More = 1, Same = 0, Less = -1), however the \ does a 'triangular reduction' which produces a list of each calculation instead of the end result, e.g. (More More Same Same More Less Less More) -&gt; (More 2 2 2 3 2 1 2)
minmax returns the range of smallest..largest, effectively removing duplicates. (More 2 2 2 3 2 1 2) -&gt; Order::More..3
+ just returns the length of this range (list), which is the result