Music in the early days was often written as a skelaton of the melody, where the performer was expected to provide the improvisation to make the tune more interesting. Many times the better or more renowned musician had his reputation based on his ability to embellish. In the 15th century, composers began to write in the ornaments as a guide to the player. Toward the end of the 17th century, most music was written exactly as it was to be played. By the Romantic period, a performer was not allowed to put in any of his own ornaments and to do so was considered a practice bordering on musical sacrilege.
It is not only proper but required that the musician play his own ornaments in the compositions of the old masters. It is, however, improper to overdo it. Modern editions have either the symbols or the ornaments written in them or have the actual embellishments provided by the editor/arranger.
The matter of ornamentation is a very personal one. If you feel that a trill belongs in a certain place . . . put it in . . . but beware of interfering with the fabric or feel of the piece. If you believe that an indicated embellishment does not belong, leave it out.
If an unspecified ornament belongs in a piece, it is sometimes indicated by a + over the note. The + can be a trill, mordent, inverted turn . . . etc. This means that the composer wants something there but doesn't care what. Some ornaments have undergone changes in the manner of executions. You must use the proper style according to the period of the music.
The prudent use of embellishments will make your performance more interesting and give you a chance to dazzle your audience with your brilliant execution. In the old days, if a player jazzed up pieces with his grand executions, the fun-loving listeners of the day would want him rewarded but if he went too far in his executions, the fun-loving audience would want him executed or at least censured for his exhibition of bad taste.
A final note: These figures are not strictly counted but felt. Don't change the timing of the piece just to fit an ornament in. For example, a trill on a quarter note in 4/4 time lasts exactly one beat no matter if it is played in sixteenths, thirtyseconds or triplets. A slow trill and a fast trill last only as long as the note they are indicated on.
1. The Trill is executed by rapidly alternating between the base note and the note above. This is the most important embellishment. It is sometimes quite difficult to find a comfortable fingering on the recorder. Experimentation and practice will make it easier. Remember to use the I II and III fingerings to facilitate playing..
TRILL
2. The Mordent is fundamental to much early music. It has gone out of style but will often be encountered up to the Late Rococo period.
MORDENT

3. The Inverted Mordent is also common.
4. The Long or Double Mordent is often used in early music. It is essentially two mordents played one after another. Notice that the figure starts on the note above the base tone.
LONG MORDENT

5. The Grace Note or ACCIACCATURA is important in all music up to the present. Be certain to play them exactly on the beat of the note.
6. The Long Grace Note or APPOGGIATURA is common to early music when the rules of harmony did not allow dissonance (notes outside of the chord structure). They are really just a shorthand writting of a rythmic figure. Note that they look like an Acciaccatura except for the slash on the stem.
LONG GRACE NOTE

7. The Turn or GRUPETTO generally is applied to music from the Renaissance to the Romantic period. Up to about 1775 it is executed thusly.
TURN
8. The Inverted Turn is rare but you may sometime encounter it. Once again the execution up to about 1775 is presented.
INVERTED TURN

9. The Turn when it is placed after a note is played like this. Notice in the above examples, the turn is placed over the originating note.
TURN after the note

10. The Inverted Turn, once again rare, placed after a note is played as follows.
TURN after the note

11. After about 1775 during the transition from the Rococo to the Romantic period (sometimes called the "Classical" period) the execution of the turn is played as a 5 note group (quintuplet).
CLASSICAL TURN

12. The Inverted Classical Turn is very rare. Play it in this manner for pieces after the Rococo.
INVERTED CLASSICAL TURN

13. All embellishments can be acted upon by accidentals above and/or below the symbol. The accidental does not affect any other notes in the measure.
Play the following tune with all the embellishments. There are no Inverted Turns but plenty of challenge. Practice the turns in both the old and new styles.
To hear the Old Professor play this piece on his beautiful Adler alto recorder, CLICK HERE.