Singing practice:

simple and effective advice for choir singers (voice teacher)

very good short instruction videos from operatic tenor Christopher Jacklin

very useful and entertaining instruction videos from voice coach Madeleine Harvey

Vocal Ease, a great app for vocal warmup and vocal excercises. Have a professional voice teacher in your pocket, for the price of a coffee. Version for Android. Version for iPhone.

Ear training:

Hear music like Paul and Philip do (well, after a lot of practise) with this

functional ear trainer for PC (android phone or iphone).

It teaches how notes sound in harmonic context, in relation to the tonic.

Music Theory:

Free course from the Open University that gives an understanding of musical theory and notation. It is "pitched" at a level equivalent to grades 1-3 of the Associated Board of the Royal Schools of Music theory exams.

Simple step by step guide to learn how to sight sing using solfege (Do Re Mi).

It's simple, but again, you need lots of practise.

Intonation:

A great way to hone your intonation, i.e. singing in tune, is to practise singing single notes (and eventually your lines) over a drone, set to the base note or tonic of the passage. That way you learn to both hear and sing the notes of the scale in relation to the tonic. Also you get to know the sound of intervals.

Here is a free online drone, for producing a sustained drone tone, if you don't have a keyboard with organ setting.

Interesting article on why a capella pieces are hard to sing in tune.

Vocal technique:

Some more detailed and technical articles on vocal technique, for further reading.

Singing with an 'open throat' - Vocal tract shaping (singwise.com)

Converting Midi files:

Though imacs, ipads, iphones etc can't read midi files directly, you can convert

them online. Here's one site:

www.conversion-tool.com/midi

[choose "don't add to public database", and I suggest turning off Chorus

and Reverb]