What does this notation (bar joining notes) mean?

Specifically I'd like to know about the apparent joining of a dotted quaver and a semiquaver in the second row of my photo.

Is that what these are?

If that is what is meant then how does this differ from a separated dotted quaver and semiquaver?

You're right it's just a dotted eighth note and a sixteenth note. The bar across the top is called a beam and it is typically used to group smaller notes by beats. For example that pattern in 4/4 would take up one of the four quarters note beats. Grouping them together clearly shows they make one beat in 4/4.

• It's perhaps worth noting that in vocal music beams are not generally used, unless the notes are sung on the same syllable. This might be why the OP was surprised by them; to a pianist this is the only way of writing it. – Brian Chandler Feb 20 '15 at 12:24
• Except in the last 50 years, when the antique practice of beaming by syllable has almost completely died out. Good thing too. It could have been largely responsible for singers' notorious inability to read rhythms. – Laurence Payne May 19 '16 at 12:27

As Dom says, it's a beam. Beams will join notes (as long as they are smaller than crotchets!)to make patterns of beats. In 4/4 time they should join any appropriate notes to split the bar into 2 equal halves. It's not always written like that these days - but it does make things easier to read. Likewise, in a 2/4 bar, a beam would stretch for the equivalent of each beat. If the note values were small, they may go over each separate beat in 4/4.

• Tim can you expand on this a bit? What is a crotchet? Why do we have to split the bar into 2 EQUAL HALVES? Did you mean in 2/4 time a beam would equal one beat? But in a 4/4 they may extend beyond just one beat? I was hoping that notes joined by a beam would always equal one beat (time value of a quarter note in 4/4). Now I'm confused. – Rockin Cowboy Feb 20 '15 at 0:49
• @RockinCowboy - a crotchet si what we in England quaintly call a one beat, or quarter note.Splitting a 4/4 bar in two 2 beat parts often makes it easier to read, and was an old 'rule'. Often, in 4/4, if one half of a bar has 4 quavers (1/8 notes), they will be joined by one beam. Unequal notes tend to have a beam over one beat's worth. – Tim Feb 20 '15 at 9:36

The "rule" is that beaming and note grouping should not obscure the beat. In particular it should not obscure the mid-point of a 4/4 bar. These rules can serve us well, but are also routinely broken :-)

(Has to be an Answer because of the necessary picture attachment)